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Union Pacific Early EMD Switchers

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This page was last updated on June 26, 2013.

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NW2s

Union Pacific's first Diesel switcher arrived in late October 1939 in the form of an Electro-Motive Corporation (EMC) demonstrator model NW2 and began an association between the railroad and the builder that continues today with the delivery of the newest SD60Ms. UP's first NW2 was equipped with EMC's own, new in 1939 12-cylinder 567 Diesel engine, which in combination with EMC's own electrical equipment produced a 1,000 horsepower yard switcher. While this was Union Pacific's first experience with Diesel yard switching motive power, UP had previous experience with EMC as the supplier of Diesel engines for its Streamliner fleet, built between 1934 and late 1937. UP Streamliners M-10001 through M-10006, along with the two City of Los Angeles and City of San Francisco E2 A-B-B sets were all powered by EMC's Winton Model 201-A Diesel engines. The story of the design change from the in-line Winton Model 201-A engine to EMC's entirely new, V-type 567 engine was related by Preston Cook in the Part II of his excellent FT article in November 1989 Railfan magazine, in which he told of the successful engineering that went into the new design, and how production began in late 1938. Union Pacific's two EMC E3As (the first of that model built) were delivered in March 1939 with EMC's new 567 Diesel engine, making them the railroad's first experience with the new prime mover.

When Union Pacific and Electro-Motive agreed to the demonstration of the EMC NW2 demonstrator number 889 (also its builder serial number) in October 1939, it may have been because of what UP saw as competitive pressures. Arch-rival Santa Fe already had its first Diesel switchers, delivered as thirteen NW2s in May through September 1939. Competitor to the north, Great Northern, received its first 567-powered Diesel switchers, as GN SW1 5101 and NW2 5302, in January and February 1939 respectively. Even the Gould trilogy, the Missouri Pacific, the Denver and Rio Grande Western, and the Western Pacific, with their combined route between Kansas City and Oakland, signed on board as customers for EMC's two new Diesel switchers, the SW1 and NW2. Western Pacific SW1 501 was delivered in late September 1939. Fellow Gould descendent D&RGW didn't get its sole NW2 (its first Diesel) until late January 1941, but Gould-sibling Missouri Pacific bought its first all-EMC switcher as its road number 9104, accepting delivery in September 1939. UP's former Harriman co-dependent Southern Pacific didn't buy NW2s until after UP was already running its first NW2s (SP's first 10 NW2s were delivered in June and July 1941 as SP 1310-1319), but SP did have experience with the smaller SW1, having bought its first 567-powered switcher as SW1 1000 in April 1939. Other SP SW1s soon followed, as SP 1004-1009, in November 1939. When compared with its competitors and neighboring roads, UP again proved its motive power conservatism, and bought after everyone else, letting them test the waters and sort out the problems.

By late 1939 Union Pacific was in need of a more modern fleet of yard switchers. Most of its steam switcher fleet was between twenty-five and thirty years old, with the newest being at least eighteen years old. However, the arrival of Diesel switchers did not spell the immediate end of UP's steam switcher fleet. The sudden growth of World War Two related traffic allowed only minimal retirements of the steam switcher fleet to take place. The delivery of the twenty-five unit order for NW2s in 1947 was really the first big blow to the then 126-locomotive steam switcher fleet. This group of 1947-built NW2s brought the total Diesel switcher fleet up to 141 units, which included the seventy-six NW2s, along with fifty-four ALCo S-2s, five Baldwin VO1000s, five Fairbanks-Morse H10-44s, and UP's single GE 44-tonner.

The EMC demonstrator 889 was built in October 1939 and sold to UP as their D.S.1000 in March 1940. The road number included "D.S." (for Diesel Switch) as part of the railroad's locomotive identification scheme which reflected UP's desire to segregate its "motorized" locomotives from its steam locomotives. By the late 1930s, the fleet of remaining McKeen and other gasoline motor cars were operating with an "M" prefix, and the Streamliner fleet would soon be renumbered to include an "M" in the road number to designate them as "Motor" sets. The "D.S." designation was used to separate the steam switching fleet from the Diesel switching fleet. The new NW2 demonstrated on UP as EMC road number 889 for the entire six months after being built, and prior to being purchased. UP D.S.1000 had EMC order number E308, which it shared with the later nine units, UP D.S.1001-1009. There are two possible explanations for this shared order number, and without documentation, we can only speculate. First, UP may have originally intended to purchase ten NW2s, and the EMC demonstration was merely a way to work out the bugs of Diesel switcher operation prior to committing a larger sum of money for the actual purchase. A second explanation comes from examination of EMC and EMD builder records. EMC 889 may have been built under a separate order and had its order number changed to match the later follow-on order for nine additional units, delivered as UP D.S.1001-1009. The builder record shows that EMC/EMD has a documented history of changing the order number, and sometimes the builder date, of its demonstrators upon their sale (ostensibly for warranty purposes). Research has also found that EMC/EMD assigned a unique five-digit engineering number to each one-only test and/or demonstrator locomotive, apparently before construction began and before the assignment of the builder serial number. Other research has shown that the order number for a single unit order (or a multiple unit order) may change to reflect changes in financial arrangements for each locomotive order.

At the same time that UP was using the EMC NW2 demonstrator in Omaha, the railroad was also testing an EMC SW1 demonstrator, EMC road number 911, whose road number, like the NW2 demonstrator, matched its builder serial number. UP most likely found that the SW1 was both too light and underpowered for its intended use, much like today's SW10s are considered to be underpowered for most tasks. The SW1 was returned to EMC in March 1940, the same month that UP formally purchased the NW2 demonstrator, and was later, in September 1940, sold to Great Lakes Steel.

The demonstration of EMC 889 on Union Pacific was a success, and led to UP's order for nine more units, delivered two months later as UP D.S.1001-1009. In July 1940, five more NW2s were ordered, under EMC order number E328, and were delivered as UP D.S.1010- 1014. UP placed EMC order number E371 later in 1940 for ten more units, and they came as UP D.S.1015-1024 in December 1940 through March 1941. This gave UP twenty-five new NW2s for assignment to its various yard locations throughout its system. The improved performance and cost efficiencies of the new units were sufficient enough that UP again selected EMC for eleven more NW2s. UP D.S.1025-1035 were ordered under EMC order number E476 in August 1941, arriving on the property between October 1941 and July 1942. By the time that War Production Board restrictions took effect, and the last pre-war NW2 was completed in March 1943, Union Pacific had received thirty-six of these successful yard switchers. These thirty-six units were what has been called Phase I NW2s and were equipped with EMC's (and after January 1941, EMD's) 12-cylinder 567 engine, coupled to EMC-design D4 and D4D main generator, producing 1,000 horsepower through four EMC-design D7 and D7C traction motors. The outward appearance of the Phase I NW2s is characterized by the two-stage taper on the top of the hood ahead of the front cab wall, short exhaust stacks and the lack of hood-side louvers. All of the short-stack NW2s were later equipped with eight-inch diameter, straight-pipe extensions, some, such as the 1069, used much larger twelve-inch diameter, "fat-stack" exhaust stack extensions.

As part of EMD order E476 (UP D.S.1025-1035), on 13 August 1941 UP ordered an additional six NW2s, but the order was canceled on 7 July 1942 because of the War Production Board's limitation that EMC/EMD could build only a limited number of FT road units, which used the new 16-cylinder 567 engine. The restriction against switchers wasn't so much because America's railroads didn't need, or want, more EMD switchers, but because EMD's entire production of 12-cylinder 567s was needed to support the military uses of the new engine design, which included U.S. Navy landing craft. The Union Pacific road numbers of this canceled part of order number E476 were to be from D.S.1044 to D.S.1049. EMD assigned builder numbers 1705-1710 to the canceled units, and did not use the numbers again for any other locomotives.

EMD also assigned builder numbers 1697-1704 to eight additional units, but did not build them. This block of numbers matches what may have been assigned to an earlier NW2 group numbered as UP D.S.1036 to D.S.1043, and was also canceled by the War Production Board. Since Union Pacific still needed additional Diesel switchers to modernize its yard switcher fleet, the railroad ordered these additional switchers in September 1943 from its long time steam locomotive supplier, American Locomotive Company (ALCo), not so much because UP was all that impressed with Alco's McIntosh Seymour Diesel design, but more likely due to the fact that the McIntosh Seymour engine was not needed by the war effort, making the switching locomotives of ALCo (and competitor Baldwin) more available to America's railroads. UP's first nineteen ALCo S-2s, later road numbers D.S.1100 to D.S.1118, were delivered as D.S.1036 to D.S.1054 between September 1943 and January 1944. These nineteen units were renumbered to D.S.1100 to D.S.1118 in May and June 1945 to make way for additional NW2s in the form of D.S.1036 to D.S.1050, delivered in May to July 1946. Later ALCo products were purchased by Union Pacific, including an additional thirty-five S-2s, forty-five S-4s, and minimal quantities of RS-2s, and RSC-2s, but the reliability problems of the ALCo engine design UP experienced with the 1500- and later 1600-class FA and FB road units led UP to concentrate on EMD products for subsequent road and switching locomotive orders.

UP NW2s D.S.1000 to D.S.1035 were delivered in UP's original black switcher paint scheme. The locomotives using this paint scheme were painted black with yellow striping (white on D.S.1000) and yellow lettering, with "Serves All The West" in yellow on the left cab side and "Road of the Challengers" in red on the right side. UP D.S.1000 originally had a multi-colored "Overland" shield on its cab sides for a short period of time. All UP switchers (EMD, ALCo, F-M, and Baldwin) in the black switcher scheme were repainted to the later standard yellow and gray scheme during late 1945 and used the now standard red-with-black edging lettering. The original cab-side slogan of "Road of the Challengers" was changed to "Road of the Streamliners" at the same time.

UP road numbers D.S.1055 to D.S.1060 were originally six Baldwin VO1000s which for unknown reasons were delivered to Union Pacific numbered in reverse order of their builder numbers sequence, beginning with the D.S.1060 in mid October 1943. The subsequent road numbers arrived, continuing the reverse sequence, in October 1943 through February 1944. The six units were renumbered to UP D.S.1200 to D.S.1205 (in builder number sequence) in May 1945, again, as with the ALCo S-2s, to avoid the growing NW2 fleet.

With the end of World War Two, and the subsequent sudden increase in post-war posterity rail traffic, Union Pacific found itself in need of more yard switchers. EMD NW2 production resumed in July 1945, and UP was soon in line for additional units. Fifteen more NW2s were delivered, built under EMD order number E683, as UP D.S.1036 to D.S.1050 in May through July 1946. Within six months, the twenty-five units with road numbers D.S.1051 to D.S.1075 were ordered, using EMD order number E820, arriving between February and June 1947. The delivery of these twenty-five Diesel units allowed UP to begin the retirements of large numbers of its then-current steam switching fleet of 126 locomotives, retiring forty-nine steam switchers in 1947 alone (ten steamers had been retired in 1946 after the delivery of D.S.1036 to D.S.1050).

The final twenty units of UP's NW2 fleet, UP D.S.1076 to D.S.1095, were built in March to September 1948, using EMD order number E998. The last eight units of the order (1088-1095) were delivered with 253,000 pounds operating weight and 65:12 gear ratio for a slower maximum speed of 45 mph. Several were later changed to a more standard 62:15 gear ratio.

All ninety-six UP NW2s were delivered with a "D.S." prefix to their road numbers, denoting "Diesel Switch". In February 1953, instructions were issued to remove the D.S. prefix. At the time, thirty-three units were among those switchers assigned to the railroad's South-Central and Northwestern Districts. Of these thirty-three units, UP 1052 was the first to have the prefix removed, on 18 February 1953, and UP 1081 was the last, losing its D.S. prefix on 16 July 1953. Research has not discovered the renumber dates for the other sixty-three units.

Generally speaking, Union Pacific's NW2 fleet was assigned to the railroad's yards in the western states, with most being used in Los Angeles, Salt Lake City, Portland, and Seattle, and smaller numbers being used in southern Idaho. One of the earliest assignments, in 1943, included the new yard at Iron Mountain station in southern Utah, completed as part of the expansion of iron mining activities for the new Geneva steel plant built near Orem in the northern part of the state. The largest structure built as part of the new yard facilities at Iron Mountain, completed in October 1943, was the single stall, 68 x 17 foot, corrugated iron sheathed engine house, with attendant fueling facilities. No provisions were made for the operation of steam locomotives. Another early assignment for NW2s included the large yard at Salt Lake City, Utah. In April 1942 two work stands were constructed in the Salt Lake roundhouse specifically for the maintenance of the new Diesel switchers. Three stalls in the 1918-built roundhouse were later set aside, in 1943, for exclusive use in the maintenance of Diesel switchers, including raised platforms and small 5-ton gib cranes. Other stalls were later converted for the growing numbers of Diesel switchers and passenger and freight road power being maintained at the former all-steam facility. The total dieselization of both yard and road service on Union Pacific's Utah and California Divisions in 1948 was the major impetus for the replacement of the Salt Lake City roundhouse in 1951 with the new Diesel and Turbine Locomotive shop, completed in August 1955, which remains an important facility for the railroad today.

During 1957, a third of the NW2s (thirty-four units) were assigned to the Oregon Division. Of those, seventeen were at Portland, seven were at Seattle, and the other ten units were scattered to the smaller yards, including Hinkle, Olympia, Centralia, The Dalles, and Huntington.

Assignments for early 1964 show forty-eight units, just over half of the NW2 fleet, assigned to the California Division, which included all of California, Nevada, and Utah. The California Division assignments included UP 1052 leased to the Harbor Belt Line in Los Angeles and UP 1037 leased to the Freeport Railway at the newly privatized, former Navy Supply Depot at Clearfield, Utah. As in the late 1950s, in 1964 about a third of the NW2 fleet, in this case thirty-six units, were assigned to the Oregon Division, including UP 1004, which was leased to the Spokane International Railway. There were ten NW2s assigned to the Idaho Division and a single NW2 assigned to the Wyoming Division. Switching duties on the Kansas Division were being handled solely by products of the American Locomotive Company, such as S-2s, S-4s, RS-1s, RS-2s, and RSC-2s. The NW2s on the Northwestern District shared their switching duties with the five F-M H10-44s.

By 1975 the heaviest concentrations of remaining seventy-six NW2s (the other nineteen units had been retired) were on the South-Central and Northwestern Districts. On the South-Central District, there were fifteen NW2s at Los Angeles on the California Division and fourteen NW2s on the Utah Division at Salt Lake City. On the Northwestern District, the Oregon Division was home to twenty-nine NW2s, with eighteen units at Albina Yard in Portland, five at Seattle's Argo Yard, and three each at Hinkle and Spokane. The six NW2s on the Idaho Division were all assigned to the yard at Pocatello, and the single NW2 on the Eastern District's Wyoming Division was at Cheyenne.

Yard and switch engine assignments for March 1982 show just twenty-one NW2s remaining on the roster. The highest quantities were at Albina, with seven units, and at Los Angeles, also with seven units. Two units were at Argo and single units were assigned to Council Bluffs, Iowa and Pocatello, Idaho. Five units were stored serviceable at Albina and both Pocatello and Nampa, Idaho.

Retirements of NW2s began in 1966 when Union Pacific sold its first two NW2s, 1000 and 1001, to the Stockton Terminal and Eastern Railroad in Stockton, California in July. UP 1000 and 1001 kept their original road numbers for their new owner, only to return to the UP roster later, in a round about way. The two units became Sacramento Northern 607 and Western Pacific 608 after a trade between ST&E and Western Pacific for two WP ALCo switchers in 1970 brought the NW2s to the WP roster. The units returned to the UP roster with the 1982 merger between WP and UP. UP 1000 resides today (repainted to its original black scheme) with other examples of railroad equipment preserved by the State of Nevada, at Boulder City. UP 1001 is preserved by the Feather River Rail Society at Portola, California.

The NW2 fleet remained stable for another six years, until 1972, when the retirements began again; only three units were retired in the following years of 1973, 1974, and 1975. Thirteen NW2s left the roster in 1972 when they were traded to EMD in February and March on new SD40-2s. Two others were retired in 1972 when UP 1053 and 1067 were sold to dealer Industrial Maintenance Services (IMS, the owner of which was later to become a principle in Chrome Locomotive and later still, one of the owners of today's National Railway Equipment). IMS refurbished both units at its rented space in the Indiana Harbor Belt roundhouse in Hammond, Indiana and sold them to the Elgin, Joliet and Eastern in November 1972. UP 1020 was retired after having its cab crushed in an accident in Las Vegas, Nevada in October 1972, and was scrapped by the railroad at Omaha in March 1973.

UP 1009 was retired and sold to Precision National Corporation in November 1973. No record has come to light to show whether PNC resold the unit to one of its customers, or simply scrapped it for parts. In 1974 Pacific Fruit Express (half owned by UP) needed a switcher at its Roseville, California facility. UP 1048 was retired in October, rebuilt at UP's Salt Lake City shops and sold to PFE as their 1048 in March 1975. The unit was later transferred to the PFE facility at Tucson, Arizona. UP 1028 suffered wreck damage in Los Angeles, California in January 1975, being retired and scrapped by UP at Omaha in April 1975.

The continued retirements of NW2s began in earnest in 1976, when eight units left the roster. Seven were sold to dealer Precision National during the year, including UP 1029 which was used in PNC's national lease fleet, painted in PNC's distinctive yellow and green paint scheme. Precision rebuilt the 1045 and sold it in June 1977 to the Monongahela Connecting Railroad, where it operated in the Pittsburgh, Pennsylvania area as their number 432. The other five were most likely scrapped by Precision. The eighth NW2 retired in 1976, UP 1035, was sold to Industrial Maintenance Services, rebuilt with a close-clearance cab and sold to Ford Motor Company for service in their gigantic River Rouge industrial complex in Detroit, as their road number 12001.

Chrome Crankshaft Company in south Chicago started their locomotive rebuilding activities in 1977. Some of their first efforts included the rebuilding and resale of former UP NW2s. Of the thirteen NW2s retired by UP during 1977, six were sold to Chrome. Chrome rebuilt UP 1034 and sold it to Tuscola and Saginaw Bay; UP 1036 went to the Canton Railroad in Baltimore, Maryland; UP 1058 was sold to U.S. Steel's Fairless (Pennsylvania) Works; and UP 1071 was sold to GE for rebuild for service south of the border on the Altos Hornos de Mexico. The other two units sold to Chrome were either scrapped for parts, or were rebuilt and sold to unrecorded companies. UP 1011 was retired in July 1977 and donated to the State of Utah's Department of State Parks and Recreation, for use on the Heber Creeper tourist railroad out of Heber, Utah, and remains today in operation on the newly reorganized Heber Valley Railroad. The other six NW2s retired in 1977 were all sold to Precision National, with no record of what Precision did with them.

Nine NW2s were retired during 1978. Seven were sold to Precision National and Chrome Crankshaft for their purposes. UP 1052 went into Precision's lease fleet. UP 1018 and 1068 were rebuilt for Chrome by Rock Island's Silvis shops, and resold in 1980 for service on the railroad of Jim Walter Resources in Birmingham, Alabama. UP 1019 was sold to Bargains Galore, a scrap dealer in Portland, Oregon who sometimes acted as a dealer and resold the serviceable units which they purchased. UP 1022 suffered wreck damage during 1978 and was retired by UP and sold for scrap to Inter-City Metals, also in Portland, Oregon.

Of the thirteen units retired during 1979, all went to scrap except 1075, which was sold to Peaker Services, who rebuilt the unit in their Brighton, Michigan shop, selling it to the Marionette, Tomahawk and Western in Wisconsin. UP 1087 went (via dealer Bargains Galore) to Rail Car Corporation in Colorado Springs, Colorado for lease service on the Cadillac and Lake City's operation of the former Rock Island trackage in Colorado, and now works on the Rawhide Shortline at the Rawhide power plant in north central Colorado.

All of the eleven units retired in 1980 and 1981 also went to scrap, except the 1026 and 1027, which were both sold to Bargains Galore. UP 1026 was resold to Diesel Electric Service in St. Paul, Minnesota, and UP 1027 was seen in transit in early 1982 going through Sioux City, Iowa. Seven NW2s were retired in 1982 and 1983. These seven units were also all sold for scrap -- to General Metals in Tacoma, Washington; Durbano Metals in Ogden, Utah; Erman-Howell in Turner (Kansas City), Kansas; Aaron Ferer and Sons in Omaha, Nebraska; St. Louis Auto Shredders in East St. Louis; and again to Bargains Galore, which sent its unit to Joseph Simons, also in Tacoma, for scrap. Also during 1980, UP was the source for leased switching motive power for some of its on-line customers. UP 1039 was leased to J. R. Simplot for use at their large facility at Don, Idaho, just west of Pocatello. UP 1077 was leased to Cargill, Inc., UP 1026 was leased to Kopell Grain at Long Beach, California, and UP 1044 was leased to Allied Chemical at Green River, Wyoming.

All eight units retired in 1984 (UP 1007, 1030, 1040, 1042, 1055, 1061, 1062, 1091) were sold for their scrap value. Two units, 1007 and 1042, were sold in 1985 to scrapper Erman-Howell. Both 1007 and 1042 had been assigned to Nampa, Idaho prior to their retirement in early 1984. The other six units remained retired and on UP property until 1988 when they too were sold to scrappers Southwest Railroad Car Parts, Aaron Ferer and Sons, and St. Louis Auto Shredders. UP 1007 was still on the property at the time of the arrival of the ex-P&LE MP15DCs and, although formally retired, was briefly renumbered to UP 7007 to avoid conflict with the new units' 1000 number series (the MP15DCs were later renumbered to the 1300 series).

The final year of 1985 started with just eight operational NW2s on the railroad, of an original fleet of ninety-six units. UP 1043, 1081, and 1085 were retired in February and March. UP 1043 was sold to on-line customer Pacific States Cast Iron Pipe Company in Provo, Utah in March 1985. The last five operational NW2s on Union Pacific (UP 1024, 1080, 1086, 1092, and 1095) were all retired on 14 April 1985. These last five units, along with six others previously retired, were all sold for scrap in 1985 and 1988: UP 1024, 1080, 1092, and 1095 went to Erman-Howell in 1985; UP 1081 was sold to Southwest in January 1988; as did UP 1085 and 1086, which went to St. Louis Auto Shredders, along with previously retired 1030, 1039, 1055, and 1061.

The retirement of those last five units in April 1985 brought to a close, the 45-year operational career of the NW2 model on UP, and with the movement of final seven NW2s to their respective scrap yards in early 1988, the saga of the EMD's pioneering NW2 switcher came to an end on Union Pacific.

As mentioned earlier, UP 1000-1035 were Phase I NW2s. Improvements between the Phase I and Phase II units included the 12-cylinder 567A engine in place of the basic 567 engine, along with the taller, conical exhaust stacks. The introduction of the D15A generator and the D17B traction motor brought on the Phase III NW2, with its outward addition of six vertical rows of louvers on the hood doors. UP 1036-1050 were Phase II units, and UP 1051-1075 were Phase III. There were no mechanical differences in the Phase IV NW2 designation, other than the availability of Schedule 6BL air brakes replacing the previous 14EL schedule. The pioneering locomotive magazine, Extra 2200 South, in its July-August 1973 (Issue 41), used the Phase IV designation because of the introduction of a 12-inch louverless "letterboard" on the hood side, running through the vertical rows of louvers. The removal of these louvers allowed the customer railroads to better display their names on their yard switchers without the difficulty of having to fit their lettering over the louvers. Union Pacific's last twenty NW2s, UP 1076-1095, were Phase IV units. Like many of the transition models, the Phase V NW2 (none were owned by UP), was very similar to Phase I of the follow-on model SW7, with the major difference being that the NW2 version had the short radiator fan intake section on the front of the unit. The Phase V NW2 also did away with the two-stage taper at the rear of the hood, just ahead of the cab. These carbody changes were a reflection of the transfer of switcher production to EMD's new Cleveland Plant No. 3 in late 1948.

Union Pacific received its last NW2 in September 1948 with the delivery of road number 1095, prior to the beginning of switcher production by Cleveland. The NW2 was succeeded in the EMD catalog by the SW7 in October 1949, after 1,119 NW2s had been built (UP's ninety-six units represented 8.5 percent of production). The design changes included the introduction the D15C generator and the D27B traction motor. These two features were also available during the production of the last Cleveland-built NW2s, but the model change (concurrent with the introduction of the GP7 road switcher) included the change in the radiator section design, from the NW2's twin 34-inch belt-driven radiator fans (and attendant short radiator intake and shutter assembly) to a larger, single 54-inch (also belt-driven) radiator fan, with its full height intake and shutter assembly. The belt driven 34-inch fans used on the NW2 were identical to those used on the FT freight locomotive and EMC/EMD's passenger locomotives from the E3 to the E7, all of which were also belt-driven. The radiator outlet on the top of the hood of the new SW7 remained as louvers, similar to those on the NW2s, until about April 1950 when these louvers were replaced by grilles made up of open wire grid, commonly called "chicken wire". This change in the hood-top features is a major design difference between the Phase I and Phase II SW7. Another is the change in the cab window design, from the arch-top design on the front and rear cab windows to more modern rubber-gasketed squared corners design. Union Pacific's SW7s were the Phase II version of this popular EMD switcher.

(click here for the final UP NW2 roster)

SW7s

UP's twenty-five SW7s were delivered in the by-then standard yellow and gray paint scheme, between August and November 1950 as road numbers D.S.1800 to D.S.1824 (with the D.S. prefix to the road number, connoting Diesel Switch), under EMD order number 4038. These twenty-five units represented just five percent of EMD's 493-unit SW7 production. Like the last twenty NW2s, these new SW7s were also delivered with the 45-mph slow speed 65:12 gear ratio and later changed to the more standard 62:15 gear ratio. None of the SW7s were assigned to the South-Central or Northwestern Districts during 1953, for which records exist for the removal of the D.S. prefix, but photograph research has shown that these units also lost their prefixes during the same general 1953 timeframe.

During mid-1957 there were seven SW7s assigned to the Oregon Division, working the switching duties in the yards at Hinkle, Baker, and The Dalles, Oregon, and in Tacoma and Seattle, Washington. UP 1812 was assigned to the Pilot Rock Branch. By early 1964, UP's SW7s were assigned only to the Idaho Division, with fifteen units, and the Oregon Division, with ten units.

By September 1975 the 25-unit SW7 fleet was spread out a bit more, reflecting the beginnings of retirement for the thirty-year old NW2 fleet. One unit, UP 1808, was assigned to the Wyoming Division at Cheyenne. Five units were on the California Division, with all of them working at Salt Lake City, including two units in the Salt Lake City Shops on September 30th. Seven units were on the Oregon Division, including one unit at Portland's Albina Yard, two units at Seattle's Argo Yard, two units at Spokane, and one unit each at Hinkle and La Grande. The remaining eleven units were assigned to the Idaho Division; five units were at Pocatello and six units were at Nampa. UP 1822 was assigned to the Camas Prairie Railroad at Lewiston, Idaho.

The retirements of UP's SW7 fleet began in early 1977 with the retirement of UP 1809, which was retired and sold to Chrome Crankshaft in February. As part of its new entry into the locomotive rebuild market, Chrome had the former UP 1809 rebuilt by Rock Island's Silvis shops and later, in August 1979, sold it to Illinois Terminal Railroad as their 1220. UP 1819 was retired in May 1978 and sold to Precision National in October 1978. UP 1803 was retired in December 1978 and sold to Chrome a year later. Chrome later sold it to Air Products Company in Pace, Florida.

By the late 1970s, Union Pacific was in need of a more modern and more reliable switcher fleet. In mid 1978, as a mechanical employee of UP at the Salt Lake shops, this author submitted a suggestion that would upgrade the SW7 and SW9 fleet with 645 engines, improved electrical controls, and electric radiator fans to replace the troublesome mechanical radiator fans. It is unknown if his suggestion was accepted (it was not acknowledged), but during August 1978 the railroad's Mechanical Department began the development work on what would become the unique-to-UP SW10 switcher. Because the first SW10s were rebuilt from UP's SW9 fleet, more information on the SW10 design will be presented later. However, the similarity in design between the SW7 and the SW9 allowed Union Pacific to also use its SW7s as part of the SW10 rebuild program. While the component layout design of the SW7s required some adjustments to allow their use in the SW10 rebuild program, the age, mechanical design, and component layout of the NW2s prevented them from even being considered as candidates.

Nineteen SW7s were rebuilt to SW10s. The first SW7 to enter the program was 1817 when it became SW10 1231 in February 1982. The others followed throughout 1982 and 1983. The last SW7 to become an SW10, and the only one in 1984, was UP 1805, rebuilt to SW10 1260 in July 1984.

The yard switcher assignments for the nine remaining operational SW7s in March 1982 saw five units assigned to the Idaho Division, UP 1813 was at Pocatello, and UP 1801, 1805, 1815, 1820 were assigned to Nampa. All of the other four units were assigned to the Oregon Division: UP 1816 and 1821 were at Albina Yard in Portland, UP 1811 was at Argo Yard in Seattle, and UP 1818 was at The Dalles. UP 1800, 1802, 1804, 1807, 1808, 1810, 1814, 1822, and 1823 were stored at Council Bluffs, Iowa awaiting rebuild to SW10s, with UP 1806 and 1824 actually in Omaha shops undergoing their transformation to SW10s.

Six of UP's SW7s were not rebuilt to SW10s. Three of those six units (1803, 1809, and 1819), as already mentioned, had been retired before the SW10 program was begun. The remaining three units not previously retired, or rebuilt to SW10s (UP 1811, 1812, and 1818), were retired in 1986, 1981, and 1984 respectively. UP 1812 was retired in early October 1981 after donating its cab to the repair of wreck damaged SW10 1205 in July 1981. The 1812 had originally been selected to be the first SW7 to be rebuilt as an SW10, but during it's strip-down, UP discovered that the SW7s differed slightly from the SW9s, and would require adjustments to the SW10 design to allow their entry into the program. While 1812 sat, stripped and waiting to become an SW10, the 1205 entered Omaha shops for wreck repair, at which time the 1812 lost its cab for the repair of the 1205. The remainder of 1812 was scrapped by UP at Omaha, Nebraska during October 1981.

On January 28, 1983, UP 1818 was involved in a wreck at The Dalles, Oregon that sheared its cab off. The unit was retired in June 1984 and over the following three years was stripped of any usable parts at the Omaha shops to support the SW10 program. In April 1987 its remains were loaded on a flat car and sold to Precision National, being shipped to PNC in early August 1987.

The last operating SW7 on UP was the 1811, assigned to Argo Yard in Seattle, Washington. This last example of the SW7 model on UP was retired in January 1985 and sold for scrap to Durbano Metals in Ogden, Utah in February 1986.

EMD ended SW7 production in January 1951, with formal production of its replacement, the SW9, beginning two months earlier, in November 1950. The design differences between the SW7 and SW9 are minor, but include a change in the bell mounting bracket, installation of the EMD standard "knuckle-buster" hood door latches, and changes in the hood side handrail and lifting eyes. The internal changes included transition from the 12-cylinder 567B engine to the later 567BC engine. With the introduction of the SW9, EMD also did away with the last of the fabricated simulations of a cast frame, a holdover from the pre-World War Two days when a welded frame was deemed inferior to a cast frame. The NW2 (for Nine hundred horsepower, Welded frame) had included many features to simulate a cast frame, but these features were gradually deleted from EMD switcher frame design after switcher production was shifted to Cleveland. One of these final "cast frame" features was the enclosing of the step treads on the front and rear of the unit. With the beginning of Phase II SW9 production, a portion of the vertical risers on these step treads were left open to allow easier inspection of the draft gear at each end of the locomotive.

(click here for the final UP SW7 roster)

SW9s

The forty-two SW9s owned by UP came in two separate orders and were all of the Phase II design. The first twenty-two units were delivered as UP 1825-1846 in April 1953 and were assigned EMD order number 4133. The final twenty units arrived, as the last of 163 early EMD NW2, SW7 and SW9 switchers on Union Pacific, with road numbers 1847-1866 on UP property in October and November 1953. These last twenty units were built using EMD order number 4216, being some of the last SW9s built by EMD -- SW9 production ended just a month later, in December 1953, after EMD had produced 786 units (of which UP's 42 units were 5.3 percent of production). These forty-two SW9s, like the twenty-five SW7s and last order of twenty NW2s before them, were also equipped with the 45-mph 65:12 gear ratio and also later changed to 62:15 gear ratio. The operating weight for UP's SW9 fleet was 235,600 pounds. All forty-two units were equipped with EMD's 567BC Diesel engine, along with the D15C main generator and D27B traction motors.

Assignments for July 1957 found seven SW9s assigned to the yards at LaGrande, Hinkle, Seattle, and Albina on the Oregon Division. The other thirty-five units were assigned to other divisions, and following the pattern for the NW2s and the SW7s, many were assigned to the California and Utah Divisions.

One particular SW9 found a very unique assignment. The purchase in 1959 of the former Bamberger Railroad's line between Hill Air Force Base and Ogden in northern Utah also included the purchase of their one-only RS-1M locomotive. Although the unit had an EMD engine replacing its troublesome ALCo engine, it retained its GE electrical gear. UP decided to transfer the modified RS-1 to its Eastern District and replace it with another unit. SW9 1864 was selected and equipped with solid front and rear road-service pilots, along with classification lights and number boards for its new assignment on this new 7-mile long branchline, which was operated from within the yard limits of the Ogden terminal. At least two other SW9s were also equipped with similar road service pilots, albeit less substantial than those on the 1864.

The switcher assignments for February 1964 show twenty units of the SW9 fleet assigned to the Wyoming Division (which included Ogden, Utah's East, or Riverdale, Yard) and four units leased to the Ogden Union Railway and Depot Company, the owner of the joint UP/SP Ogden, Utah terminal. Six SW9s were assigned to the California Division, operating in the yards at Los Angeles, Salt Lake City, and Provo, Utah. Three SW9s were assigned to the Pocatello yard on the Idaho Division, and the remaining nine units were assigned to the Oregon Division yards at Argo, Albina, and The Dalles.

The end of 1973 found the SW9s operating in a more system-wide pattern, as part of the remaining 150 switchers, again, as with the SW7s, reflecting the retirements of the more ubiquitous NW2s and the total retirements of the remaining ALCo, Baldwin, and F-M switcher fleets. Five units were operating in the Omaha/Council Bluffs terminal. On the Wyoming Division, three SW9s were assigned to the yard at Cheyenne, Wyoming, and four were assigned to Riverdale Yard in Ogden, Utah. On the California Division, Salt Lake City was the home for nine SW9s, and UP 1846 was operating at Provo. Three other SW9s were also assigned to Los Angeles. The Pocatello terminal on the Idaho Division had just a single SW9, UP 1832, and Nampa also had a single unit, UP 1831. Portland's Albina Yard on the Oregon Division had two SW9s, UP 1829 and 1834, with 1827 and 1835 in the shop there. Argo Yard in Seattle had 1838, Tacoma had 1830, Hinkle had 1836 and 1842, and Spokane was home for the 1828. UP 1833 was assigned to Walla Walla, Washington, and 1855 was at Yakima. Of the SW9s assigned to local service, 1843 was on the Ogden-Hill Field local, 1852 was on the St. John Local out of Salt Lake City, and UP 1839 was assigned to the Olympia, Washington beer local.

Six SW9s were retired prior to 1978, when the SW10 rebuild program began. The other thirty-six Union Pacific SW9s were rebuilt to SW10s. The first SW9 to leave the roster was UP 1830 which was sold to Industrial Maintenance Service (IMS) in September 1976. IMS sold the unit to Youngstown and Northern as their 302. The unit later became Union Railroad's 588, and still later, became a Birmingham Southern unit, keeping 588 as its road number.

UP 1863 was retired and sold to Chrome Crankshaft in February 1977. The unit remained on UP property until Chrome asked that it be shipped to ICG's rebuild shop in Paducah, Kentucky in mid May 1977. ICG rebuilt the unit to Chrome's specifications and in July 1977 Chrome resold it to Weyerhauser Timber D-21, operating out of Mount Pine, Arkansas.

UP 1827 and 1842 were retired in July 1977 after both units were wrecked in the same month at Albina Yard in Portland, Oregon. Both units were sold to Precision National Corporation in October 1977. No record has come to light of what Precision did with the 1827, but Precision resold the ex-UP 1842 to Tacoma Municipal Belt Line Railway in Tacoma, Washington as their 1200 in July 1978. The Belt Line later, in August 1993, sold the unit to Mount Vernon Terminal in Mount Vernon, Washington, where the unit remains in operation with its Belt Line road number. In November 1978, wreck damaged UP 1845 was retired and Chrome Crankshaft.

In addition to those six units just mentioned as being retired before 1978, UP 1848 was retired in August 1978, but was reinstated to the roster and rebuilt to the first SW10, with work starting in October 1978. UP SW10 1848 was released from Omaha shops on 2 August 1979 and was renumbered to UP 1200 on 13 March 1980 after UP decided in January 1980 that the SW10s differed enough from the SW7s and SW9s to warrant their own, new number series.

UP 1831, 1839, and 1846 were also retired in 1978, and along with the 1848, were also reinstated to the roster and rebuilt to SW10s. The 1839 was finished as an SW10 in November 1979, then renumbered to 1201 in April 1980. UP 1831 and 1846 were completed as SW10s, with their 1200 series numbers applied upon completion as SW10s 1210 and 1220 respectively. Subsequent SW7s and SW9s rebuilt to SW10s were not retired prior to their entry into the rebuild program.

The SW10 rebuild program began in August 1979, with the completion of the 1848, and continued through December 1984, with the completion SW10 1274, which was rebuilt from WP SW7 606. The last UP SW9 to enter the program, UP 1838, was completed as SW10 1265 in September 1984. The rebuild included the installation of new EMD 645 power assemblies in place of the original 567 assemblies, along with new wiring and updated electrical gear, and most noticeable of all the changes, a new radiator section with twin electric radiator fans replacing the older, single 54-inch fan, powered by drive belts driven off of the Diesel engine. The twin 36-inch radiator fans, and radiator intake wire grille and shutter assemblies were taken from retired GP7s and GP9s, as were the engine-room equipment racks used on the SW10s.

With the start of the SW10 program in 1978, all of the remaining SW9s were rebuilt into the new switcher, with the exception of one. In early 1981, UP 1843 entered the rebuilding program but was found to have a cracked frame and misaligned front bolster. With the availability of numerous SW7s as candidates for the SW10 effort, 1843 was retired on March 30, 1981 and scrapped by UP at Omaha.

(click here for the final UP SW9 roster)

TR5 Transfer units

Concurrent with normal end-cab switcher production, EMD also produced a "Transfer", or "TR", version, with a normal end-cab switcher as a lead unit, or "Cow", attached to a cabless booster, or "Calf", making a heavy switching locomotive with double the horsepower. The matching Transfer locomotive for EMD's NW2 switcher was the TR2, with the SW7 version being the TR4 and the SW9 contemporary being the TR5. Union Pacific chose not to order either the TR2 or the TR4 versions, possibly because of the high numbers of 2-8-0s and other small steam locomotives still in service on the railroad during the late 1940s. However, by the time 1950 rolled around, and the SW9 was in production, UP found itself in need of Diesel version of a non-road service, heavy switcher.

UP 1870-1877 and 1870B-1877B (eight A-units and eight B-units) were built in September and October 1951 (between UP's SW7 and SW9 orders) and were assigned EMD order numbers 6284-A and 6284-B. According to a news item in a mid-November 1951 issue of Railway Age, UP's eight TR5s were to be initially assigned to southern California. The news piece stated that six of the eight units were specifically for heavy switching in the San Bernardino yards, and the other two were for helper service on the 2.2 percent grade Cima Hill, operating out of Kelso. The use of the TR5s on these helper grades allowed UP to re-assign the 1947-built Fairbanks-Morse H20-44s to the Northwestern District. The new yard at Hinkle, Oregon had just gone into service and the F-Ms were needed to support the increased use of Diesels on the two divisions, the Oregon and Idaho, that make up the Northwestern District.

All of the TR5 sets were delivered in UP's yellow and gray, with "D.S." prefix on their road numbers. Seven of the eight TR5 sets were operating on the South-Central District (UP 1876 and 1876B were not) when their "D.S." road number prefixes were removed in February and March 1953.

Throughout the 1950s, the cow/calf sets were used in helper service on Cajon Pass and on Cima Hill, operating out of San Bernardino and Kelso, California, respectively. At least one TR5 set was also used at Caliente, Nevada for helper service on the two percent grade through Clover Valley Wash, near the Utah/Nevada stateline. These heavy duty switchers were delivered with AAR switcher trucks, equipped with cast iron brake shoes. UP soon discovered the limitations of the braking capacity of these heavy switchers when used to occasionally retard a downbound train, along with the times in which the units were returning light down hill on these steep grades after helping an upbound train. The combination of the stiff suspension of the switcher trucks and soft cast iron brake shoes soon began causing overheated wheels and overly rapid wear of the brake shoes themselves on the TR5s. To minimize some of the costs associated with the use of what were essentially yard switchers in helper service, in late 1952 and early 1953 the TR5 A-units were equipped with dynamic braking. The addition of this EMD-designed feature included a single 36-inch fan, and four resistance grids, one for each of A-units' four traction motors, installed in an enclosure added to the top of the carbody, just ahead of the cab, blanking out and covering the front cab windows. Because the feature was meant solely to retard the downhill descent of the "light" locomotives, no provision was made for the use of dynamic braking on the cab-less booster units. Due to the limited capacity of the dynamic braking (used only on the cab units to control the speed of their downhill descent), along with the added maintenance for the dynamic braking components themselves, the usefulness of the braking was soon outweighed the associated maintenance costs. Within a short period of time, by 1956, the dynamic braking feature was deactivated, with the components remaining installed on the units, unused.

The use of TR5s on helper service eastward out of San Bernardino was reduced considerably with the delivery of GP7s and GP9s in 1953, 1954 and 1957, but they were still regularly assigned to trains needing helpers heading up Cima Hill. The use of specifically assigned TR5 (and all other) helpers in the desert helper districts was discontinued completely in February 1959, an acknowledgement to the versatility of building block, multiple-unit Diesel operation, which allowed the "locomotive" on the head-end to be matched perfectly to the requirements of both uphill and downhill operations. The cow-and-calf sets were then re-assigned to heavy duty switching service in other locations. (The use of a single TR5 set at Caliente, Nevada for the Clover Valley grade between Minto and Islen was discontinued in late 1953 or early 1954.) UP 1876/1876B and 1877/1877B were then re-assigned to the hump yard in Pocatello, Idaho, where they were joined Baldwin AS-616s in both flat switching jobs and serving as motive power for the hump itself.

By February 1964, UP 1870-1875 and their respective B-units were still assigned to the California Division, being used as heavy switchers. During 1965, the 1874/1874B was working on the 10-mile, 2.3-percent Blue Diamond Spur in southern Nevada. The last two cow-and-calf sets, 1876 and 1877, were working on the Idaho Division, on the hump yard in Pocatello. Soon after, UP 1870/1870B to 1873/1873B were assigned to the hump yard in North Platte, Nebraska. The unique dynamic braking was removed from 1870, 1871, and 1872 during September 1968 when these three TR5 sets were assigned to the new Edd H. Bailey hump yard at North Platte, Nebraska. Dynamic braking was removed on 1873 when that unit and its trailing calf were assigned to Kansas City. Two sets, UP 1874/1874B and 1875/1875B were assigned to Provo for local service between the Provo Yard and U.S. Steel's Geneva steel mill in nearby Orem, taking advantage of the new labor agreement that expanded the Provo yard limits to include Geneva, five miles away. In June 1979, UP 1875/1875B were reported as being in service on UP's Clover Local in Utah, between Salt Lake City and Clover, Utah, the location of the south area of Tooele Army Depot on UP's Leamington Cutoff. (At times, this same local was at times referred to as the St. John Local.)

After they were reassigned to hump yard and heavy switching duties at North Platte, Nebraska, UP 1870/1870B to 1872/1872B were modified with 1400 gallon fuel tanks (originally they were equipped with 600 gallon fuel tanks). The larger fuel tanks forced the air reservoirs, and attendant intercoolers, to the top of carbody. After being modified, they had 521,600 pounds combined lead- and booster-unit operating weight, an increase over the combined weight of 494,700 pounds for the other TR5 sets. All three sets were later moved to transfer switching duties at Kansas City, Kansas.

Late December 1973 found UP 1870-1873, and their B-units, assigned to Kansas City, Kansas. UP 1874/1874B and 1875/1875B were still at Provo, Utah, with 1876/1876B and 1877/1877B both still assigned to Pocatello.

UP 1876 and 1877 lost their dynamic brake housings in about 1972. Dynamic braking was removed from Provo, Utah-assigned UP 1874 and 1875 at Salt Lake City, Utah in June 1972. On the 1874 and 1875, the hood-to-cab, single slope taper of a standard EMD SW-switcher was restored to the as-built configuration. (As a new journeyman mechanic in the Salt Lake shops, the author was directly involved in this). When the Pocatello shop removed the braking enclosure on the Pocatello-assigned 1876 and 1877, the slope was reversed to negate the need to re-install the front cab windows, which had been blanked out when first equipped with dynamic braking in 1953.

TR5s 1870, 1871, 1874, and 1875 are known to be equipped for multiple unit (MU) operation. The application on the 1870 and 1871 shows that MU was added at the time most of UP's locomotive fleet were still equipped with the dual receptacle 12- and 21-pin MU controls. The application on the 1874 and 1875 were completed at Salt Lake City, concurrent with the removal of the dynamic braking in 1972, at a time when all MU controls had been converted, or were being converted, to the single receptacle 27-pin system.

During late 1975 the lead unit of the 1870 set was taken out of service due to electrical malfunctions. Within six months, the trailing unit of the 1872 set was removed from service due to Diesel engine failure. To make best use of its motive power resources, in June 1976 the two out-of-service units were retired and UP's Omaha shops assembled the unique 1872/1870B set for continued use at Kansas City, and later at Salt Lake City, Utah and at Albina Yard in Portland, Oregon.

In 1981 and 1982, UP was in the process of rebuilding its SW7 and SW9 fleet to its new SW10-design yard switcher. Because the TR5A was essentially identical to an SW9, the TR5 sets were separated, the B-units retired and laid aside, and the A-units sent through the Omaha shop rebuild program, emerging as SW10s. While 1871-1876 were completed as SW10s by September 1982, UP 1877 had to wait until March 1984 for its place in the rebuild program.

The yard and switch engine assignments for March 1982 show 1871/1871B stored at Pocatello, 1877/1877B working at Pocatello, and just the A-units of 1872 and 1875 in Omaha shops for rebuild to SW10s. UP 1870B had been separated from 1872 by this time. In June 1982, 1870B, 1873B, 1874B, and 1875B were scrapped by UP at Omaha. UP 1871B and 1876B were scrapped by September 1982. UP 1877B was retired in January 1984 and sold for scrap in March to Durbano Metals in Ogden, Utah.

(click here for the final UP TR5 roster)

Exterior changes

There were several exterior modifications that were applied to Union Pacific's entire switcher fleet. During the 1950s, as the fleet of small steam locomotives were retired, several switchers, including some of the ALCo S-2s and S-4s, were modified with classification lights, train number indicators, and ladders providing access to both features. No actual documentation has been located of units so equipped. Only photographic evidence can be used to develop a partial list at best of switchers equipped with these traditionally road locomotive features. Of the NW2s, 1078 and 1082 are known to have been equipped with train number indicators and ladders. SW7s 1807 and 1820 were equipped with train number indicators, but had extra grab irons on the left front rather than ladders; SW7 1821 had front ladders. SW9s 1831, 1843, and 1864 had indicators and front ladders, with 1843 and 1864 sharing the Hill Field branch assignment in Utah.

Several units were equipped with slatted front pilots, with full front footboards, for protection of under-locomotive components during use on the branchlines. The entire eight-unit TR5 fleet was so equipped. Other units include NW2s 1043 in July 1951 at Pocatello, 1066 and 1067 in March 1950, and the above mentioned SW9s, 1843 and 1864. SW9 1864 was the only known early EMD switcher on UP to have a solid pilot, although NW2 1043 was equipped with a full snow plow at Pocatello in 1952. This snowplow was very similar, only shorter in height, to the full plow pilots applied to many of UP's GP7s and GP9s.

Throughout the mid 1970s, and beginning in about 1973, Union Pacific began applying spark arrestors (nicknamed "beerkegs" by railroaders and "cabbage stacks" by railfans) to the top of the exhaust stacks of all its switcher fleet, which by this time was all-EMD. These spark arrestors were of the Harco brand name, manufactured by the Hapco Manufacturing Company of Spokane, Washington, and were a centrifugal design that allowed any sparks to extinguish themselves as they were circulated up and out of the arrestor assembly. Union Pacific mounted them in a unique manner, developed by the Pocatello shop. The Pocatello design was improved on, and actual installation kits manufactured by the Salt Lake City shops, that allowed for easy removal of the assembly for maintenance. Upon being rebuilt with larger fuel tanks in 1968, the TR5 sets 1870-1873 were also equipped with a slightly different version of a spark arrestor exhaust stack. Their similarity to the Harco version shows that they may simply be a different method of mounting the same spark arrestor. Not all switcher units received these Harco stacks because some were already, or were later equipped with a Farr Company (of Los Angeles) internal spark arrestor exhaust manifold.

In summary, Union Pacific's ownership of 179 early EMD NW2, SW7, SW9 and TR5A and TR5B switchers contributed greatly to the total dieselization of the railroad by early 1959. Parallel with the purchase of its early EMD switcher fleet, the railroad also purchased fifty-four ALCo S-2s, forty-five S-4s, six Baldwin VO1000s, five DS4-4-1000s, five Fairbanks-Morse H10-44s, and a single GE 44 tonner. These additional 116 non-EMD switching locomotives, making for a peak Diesel switching fleet of 289 units, allowed UP to retire their steam switcher fleet over the decade of 1947-1957.

Diesel switchers were a new technology for America's railroads, and because of the times in which they were bought, motive power practices of Union Pacific's steam era dictated the method and timing of the railroad's purchase and operational use of early EMD switchers. As the era of full dieselization arrived, operating practices changed to match the railroad's needs. By the mid 1960s as additional switching motive power was required, and rather than purchase new switchers, sufficient early road switchers, such as GP7s and GP9s, were displaced in road service and could be used to take up the slack in the need to buy more yard switchers. Along with the switcher fleet, the ranks of these displaced, early road switchers also began thinning during the early 1970s, forcing other, newer road units, such as GP30s and GP35s, to be used in switching service.

By the late 1970s, Union Pacific found itself in the position of needing a more reliable fleet of dedicated switching locomotives, with the result being the SW10 rebuild program. With the 1982 merger of Union Pacific, Western Pacific, and Missouri Pacific, and the inclusion of former WP and MP SW1500s and former MP MP15DCs into the switcher fleet, the growing need for more modern switchers came to an end. As illustration of this satisfied need, the entire post-merger fleet of 173 ex-MP early EMD switchers (141 SW1200s and thirty-two SW9s, excepting nine SW9s rebuilt to SW10s at the end of the program in late 1984) were never assigned a place in the UP motive power fleet. All of these ex-MP units were vacated from the roster by mid 1985, following the sale of sixty-nine units to Precision National in February and an additional fifty-six units, also to Precision, in June. By mid 1985 the last UP NW2 (in April) and SW7 (in January) had been retired, with the last ex-UP SW9 having been rebuilt to an SW10 during the previous September. The SW10 fleet was generally assigned to the pre-merger UP lines, with some also assigned to points on the former WP to make up for the loss of that road's own fleet of eight early EMD switchers. The former MP lines have remained the home for the ex-MP SW1500 and MP15DC switcher fleet. The addition of six SW1500s and four MP15ACs from the MKT with the 1988 merger between UP and MKT has also helped to reduce the average age of UP's switcher fleet.

The need and continued use of yard switchers on Union Pacific's seventeen-state system is slowly declining, with nine SW10s having left the roster. Unfortunately, because of space constraints, the story of how the post-merger Union Pacific has utilized its current fleet of late model EMD switchers, along with the story of the home-built SW10, will have to wait for another time. With this article, we have seen how the purchase and 45-year operation of Union Pacific's fleet of early EMD switchers truly helped bring Union Pacific into the Diesel Era.

The author thanks Mark Hemphill and Ryan Ballard for their assistance in the preparation of this article.

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