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A History of Union Pacific Dieselization, 1934-1982, Part 3

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This page was last updated on August 26, 2011.

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One-For-One Passenger Unit Trade-Ins

Between 1953 and 1962, UP received 20 passenger units—E9s 900-914, E8 925, and E8Bs 922B-925B—from EMD that were built using direct unit-for-unit trade-ins from UP. Railroad and EMD records both show the trade-in units as being rebuilt to the respective E-units. This rebuilding of an old unit to a new unit is unlikely because the mechanical layout of the early E-units and the "rebuilt" E8s and E9s, were completely different, with almost nothing reusable except truck frames and some minor parts. The rebuilding concept stemmed from a tax advantage that allowed UP, and several other railroads, to pay a reduced tax on the units, since they were "rebuilt" rather than "new." This tax loophole was closed after many industries nationwide began receiving large amounts of "rebuilt" equipment, rather than new equipment.

In the case of railroad locomotives, each unit-for-unit direct trade-in came under EMD's "trade-in credit" policy, which was figured strictly on paper. Due to the short length of time between the trade-in and when the new unit was delivered, and the mechanical differences, it is unlikely that any one part from the trade-in unit was actually used on the intended new unit. It was EMD's practice during E8 and early E9 production to assign the trade-in units' builder's number to the new unit, and to show the trade-in unit's original build date on the builder's plate, even if the new unit was built using as little as five percent of the parts from the older unit, thus UP 922B-925B, and UP 925, were built as new units but were assigned builder's numbers and builder's dates from the original trade-in units. The roster shows the actual build date rather than the build date from the builder's plate.

EMD E8s and E9s

Following the delivery of the E7s in 1946, additional motive power for the road's now-daily City trains, and for the growing number of diesel-powered secondary passenger trains, came in form of six Alco PA/PB units, four FM Erie-builts, and 15 passenger-equipped EMD F3s, all in 1947. In 1948, six more FM Erie-builts arrived, along with 12 more passenger-equipped F3s. Eight more Alco PA/PB units were delivered in 1949.

In 1950, Union Pacific received its first E8 locomotives: five cab units numbered 926-930, and five booster units, numbered 926B-930B. These 10 units were the first of an eventual fleet of 46 E8s and 69 E9s. The E8/E9-series locomotives are arguably UP's most famous passenger motive power, heading up most of its passenger trains until 1963, after which they were the road's standard passenger power, until the takeover of nationwide intercity rail passenger service by Amtrak in 1971.

EMD's E8 differed in many features from the earlier E7 (and the very similar E3 to E6 models). The two prime movers were situated differently, with the main generators of the E8 facing outward toward the unit's ends. The greatest feature difference was in the way the radiators were cooled. On the E7, radiator fans were belt-driven, and they were located at each end of the radiators, and below them, pushing the cooling air up through the radiators. The E7 used the same vertically-mounted 26-inch fans as the builder's SW1 and NW2 switcher locomotives. On the E8 (and later E9), the 36-inch radiator fans were electrically driven, and mounted horizontally on the unit's roof, above the radiators, pulling the cooling air through the radiators.

The air intake arrangement for the diesel engines was also different. On the E7s, the intake air entered the carbody immediately behind the cab, through a set of louvers. On the E8 and E9s, the intake air entered through a smaller opening behind the grille, and was pulled up through a duct into the rooftop winterization hatch by a 36-inch fan. This fan was mounted to pull air from the winterization hatch and push it into the engine roof through a filter box. The winterization hatch allowed the operating railroad to change (by use of a lever inside the locomotive engine room) the flow of intake air from direct outside air, to air that had been warmed by first passing through the radiators.

On Union Pacific, by early 1955, the E8s and E9s were experiencing cooling problems, and operating officials determined that the smaller opening on the side was restricting the amount of intake air available for the engine. The road's solution was to cut an opening in the top of the winterization hatch, immediately above the reverse-mounted intake fan. Tests of this new configuration revealed that the new top opening allowed rain and snow to be pulled into the engine room, causing electrical grounds, since the electrical cabinet was located right below the intake filter box.

UP's solution to this rain and snow problem was the road's trademark "snowshields," mounted above the extra opening in the winterization hatch. Snowshields were installed on the road's E8 and E9 fleet, beginning in 1955-1956, and continuing through the late 1950s. Based on observations by railroad maintenance personnel, these snowshields may also have served to disrupt the air flow along the top of the units, much in the same way smoke lifters did on steam locomotives. This feature is unique to Union Pacific's units, and only further research will reveal its original development and purpose. (See top view photo of a UP E unit before the modification in July 1956, in The Streamliner, Volume 8, Number 1, page 15.)

After the initial 10 E8s in 1950, additional passenger power came in 1952 in the form of two FP7s and matching booster F7 units, plus a single E8, number 925. UP 925 was the result of EMD's rebuilding of a wrecked C&NW E7A, which UP settled with C&NW for and had rebuilt to EMD's then-current passenger locomotive design.

In 1953, more E8s arrived—12 cab units and 23 booster units. Four of the 1953-built E8Bs were delivered under EMD's rebuilding program that allowed the railroads to upgrade their older motive power on a direct unit-for-unit trade-in concept that gave tax advantages to the railroads for accepting "rebuilt" units instead of new units. As already noted, in reality, very little of the trade-in unit was incorporated into the new unit. Under this program, during 1953, UP traded the four remaining 1937-built E2 booster units to EMD on four of the E8 booster units. The arrival of these E8s, and the earlier delivery of many lightweight cars, allowed UP to retire its 1936-built City of Denver trains, which were replaced in City of Denver service by a general pool of both locomotives and cars.

By the end of May 1953, UP had acquired the last of its fleet of 18 E8 cab units and 28 E8 booster units. Additional units were still needed to fully dieselize all of the road's remaining passenger trains. In October 1953, the road ordered 15 more E8s. These were to be delivered after January 1954, so in November 1953, EMD informed UP that it had improved its entire line of locomotives, which included a change in model designation. In the case of the passenger units, the E8 would become the E9. The major difference with the E9 came in the use of EMD's new 567C engine instead of the earlier 567B engine, and the replacement of the earlier D27 traction motor with the D37 design. The E9 model generated 2,400 horsepower, compared to the E8's 2,250 horsepower.

UP's first E9s were delivered in May and June 1954, numbered 943-947 and 950B-959B. In February 1955, 30 more units were ordered. UP 948-956 and UP 960B-966B were delivered in May and June 1955, with 957-962 and 967B-974B following in September and October of that year. The delivery of these newer units allowed UP to convert to freight service its older Fairbanks-Morse Erie-built units (built in 1945-1948) and Alco PA/PB units (built in 1947 and 1949), all of which had proven to be unsatisfactory in passenger service.

The need to replace the older diesel passenger power was the motivation for acquiring more E9 locomotives in 1956. EMD's "rebuild" program was still in place, and Union Pacific took advantage of it to replace its oldest passenger locomotives. The E3 cab and booster units, and the E6 cab and booster units, were all traded to EMD for eight E9 cab units (numbered 900-908) and five E9 booster units (900B-904B), all delivered between January and June 1956.

During the early 1960s, the road again found itself to be in need of more reliable passenger motive power, and the remaining E7 units were traded in on new E9s. In 1961, two E9 cab units arrived, numbered 908 and 909. In December 1962, two more E9 cab units (910 and 911), along with two E9 booster units (910B and 911B) were delivered. A year later, in December 1963, the road's last E9s arrived, when UP 912-914 and UP 912B and 913B were delivered. These later units boosted the total E9 fleet to 35 cab units and 35 booster units.

Throughout its history, Union Pacific has had occasion to operate both special passenger trains and secondary passenger trains that saw a seasonal or temporary increase in traffic. The motive power for these movements is generally called protection power. In the earlier years, the road simply used steam power for these special trains, which included mail and express trains, circus trains, troop trains, and other special moves, such as Shriners' specials and Boy Scout specials. With the retirement of large numbers of its remaining steam locomotives during the late 1950s, this need was filled by retrofitting steam generators to 15 of the 1957-built 300-class GP9 cabless boosters. By the early 1960s, the need for power for these special trains was filled by 13 GP30B units that were equipped with steam generators. Even with these 28 units still available on a standby basis, in August and September 1965, less than two years after the delivery of its newest E9s, the road acquired 10 SDP35s, the passenger version of EMD's six-axle, 2,500-horsepower SD35 locomotive. These 10 were Union Pacific's final new passenger-locomotive acquisitions.


Seven of Union Pacific's ten SD7s were purchased in mid 1953 for the Iron Mountain iron ore trains in Utah, along with heavy switching in the Provo, Utah, yard and at the yard adjoining the U. S. Steel plant at Geneva (near Provo), the destination of the Iron Mountain ore trains. The three other units were initially assigned to "to effect economical operation of various branches, other than on the South-Central District." One of these three units, UP 782, renumbered to UP 457, was used throughout its career on the Coalmont Branch, out of Laramie, Wyo., where it replaced an earlier Alco RSC-2. On that assignment, the unit was equipped with a standby water heater, with its attendant exhaust stack mounted to the upper right hood side near the radiator intakes, and snow plows on each end. The entire ten unit group was renumbered in late 1962 and early 1963 from their original 775-series numbers to the 450-series numbers.

The SD7s were in the Iron Mountain service until replaced in 1968 by new SD45s. At that time, four of the units were reassigned to North Platte, Neb., on the new hump yard there. The other five SD7s were assigned to local service between Salt Lake City and Ogden, Utah, and the Clearfield Freeport Center, midway between these two cities. During the 1970s, the Clearfield Freeport Center was the single largest traffic generating point on UP.

Five years after the SD7s began work at North Platte, UP in December 1973 mated SD7 459 with the railroad's first four-axle yard slug. This was soon followed during 1974 by two more SD7s, UP 454 and 458, being paired with the second and third UP-built four-axle yard slugs, with all three slug sets being assigned to North Platte. The SD7s were soon found to be underpowered for this heavy switching assignment and subsequent yard slugs were mated with higher-horsepower SD24s.

UP 456 was the first SD7 retired, in April 1978. UP 457, the unit assigned to the Coalmont Branch in Wyoming, was retired in August 1978 following a wreck. Four units followed in 1979: UP 450-453. Two units, UP 455 and 458, were retired in 1980. The last two SD7s to be retired were UP 454 and 459, two units mated with four-axle yard slugs. Both were retired in 1982.

Two of the retired SD7s (UP 456 and 457) were sold to Precision National Corp., and rebuilt to SD10s by ICG at its Paducah, Ky., shop. The two units were then shipped in March 1980 to Liberia in West Africa for use on the LAMCO iron ore railroad. UP 453, 455, and 458 were rebuilt by ICG to SD20s, and entered service numbered as ICG 2030, 2034, and 2032, respectively. The remaining five units, UP 450, 451, 452, 455, and 459 were all scrapped following their retirement.

EMD GP7s, GP9s and Other Early Road Switchers

Union Pacific's first road switchers were the Alco-GE RS-2s and RSC-2 s of 1947-1949. Fairbanks-Morse road switchers were delivered in 1948 and 1950, and a Baldwin road switcher also came in 1948. Road switchers were assigned to branch lines as direct replacements for steam locomotives, and with a surplus of steam locomotives available after UP dieselized its western mainline routes, the carrier did not need more road switchers for another two years.

Hoping for an order from Union Pacific, in late 1949 EMD sent its GP7 demonstrator number 200 to work in Salt Lake City. About ten months before, UP had received what would be the last of its F3 road locomotives from EMD, and EMD was selling the road switcher concept as a more utilitarian approach to steam locomotive replacement. Union Pacific apparently appreciated the road switcher design for a little over a year later, in early 1951, UP ordered six Baldwin AS-616 units. Four were purchased for heavy switching, but two others were to be assigned to branchline service in Kansas.

In late 1952, two years after the demonstration of EMD no. 200, UP ordered 10 examples of EMD's then-current road-switcher model, the GP7, which had first been offered in 1950. This first group of ten units was numbered as UP 700-709, and were delivered in February and March 1953. In May 1953, the road ordered 10 more, specifically for service on branch lines in Idaho, and for through train service in Nebraska, Wyoming, Colorado, and Kansas. Two months later, UP ordered 10 more GP7s. These 30 GP7s, originally numbered UP 700-729, were delivered between February and October 1953.

There is photographic evidence that the GP7s were originally to be delivered with UP's D.S. road number prefix, denoting Diesel Switch. A photo in the Union Pacific Historical Society's bi-monthly publication, The Streamliner, that shows UP 709 with a patch of fresh yellow paint under the 709 number on the front angled hood surface. This means that UP 709 was renumbered from something else, likely D.S. 709. This first group of 10 GP7s were delivered in March 1953, with the order to remove the D.S. prefix having come in mid February. They were renumbered to their 100-series numbers in November 1953. (see The Streamliner, Volume 11, Number 2, page 26)

The railroad found these 30 GP7 units to be so cost-effective that in October 1953 it ordered 190 more GP7s, with 115 of them to be built as cab units and 75 as cabless booster units. EMD accepted the order, but since the 190 units would not be delivered until after January 1, 1954, EMD on November 2, 1953, notified UP that a model change was under way and that they would be delivered as some of the first examples of EMD's GP9 model, the GP9 being the 1,750-horsepower successor to the 1,500-horsepower GP7. While EMD had built GP7 booster units for Santa Fe (five units in 1953), these 75 units for UP would be the first cabless booster units of the GP9 model.

After UP sent its order for the additional 190 GP7s to EMD, or maybe at the same time, the mechanical department realized that there were not enough road numbers in the 700-series to accommodate the new units without the numbers running into the 800-series steam 4-8-4 steam locomotives. To change the potential conflict, the 100-series road number group was selected. The 30 GP7s would be renumbered road numbers 100-129. The regular GP9s were numbered upward from 130 to 244, and the cabless boosters were numbered 130B-204B. UP 205-244 were built without dynamic brakes due to their planned assignment to the Eastern District. All were delivered between January and April 1954. As the initial order was arriving, UP ordered an additional 50 units, to be numbered 250-299. These were delivered in August and September 1954. In between were four units that were to be leased to the Camas Prairie Railroad, an Idaho road that UP owned jointly with Northern Pacific. These were to be numbered as UP 245-248. EMD offered GP9 245 to UP at a reduced price because it had undergone a brief demonstration on another road, and UP 246-248 were added to the same order to serve as UP's contribution to the Camas Prairie pool. A fifth unit was needed, so UP offered its number 244. But because UP 244 lacked dynamic braking, it was turned down, and dynamic brake-equipped UP 204 was selected instead. It was renumbered to UP 249 to keep the Camas Prairie units in a single road-number block.

This large fleet of 275 GP7s and GP9s, along with the road's large fleet of 237 EMD F units, brought an end to steam operations on all but UP's Eastern District. In 1957, UP took delivery on 50 more GP9 cab units and 50 more GP9 booster units, bringing to an end all of the road's regular steam operations, except for some later seasonal use. As UP President Arthur Stoddard wrote in February 1957, these locomotives would allow the railroad to "get by next fall with very little use of steam power." These 100 units, delivered from July through October 1957, were the last diesel units to be acquired until the coming of turbocharged SD24s two years later.

GP9 Turbocharging Program

Union Pacific first tested turbochargers for its GP9 fleet on locomotive 281 in December 1955. It was soon followed by GP9B 185B and GP9 261 in April and May 1956, all three units being equipped with a design developed by the AiResearch Industrial Division of Garrett Corp. of Torrance, Calif. These three units remained under test, operating in helper service on California's Cajon Pass, and later, between Salt Lake City and Los Angeles, until early 1959. Based on favorable results from these tests, UP began a formal program to add three different turbocharger designs to some of its newest road freight diesels—its 100-unit fleet of 1957-built GP9s/GP9Bs, which had been numbered in the 300 series. Beginning in March 1959 and continuing throughout that year, three A units (302, 318, 331) and six B units (303B, 306B, 311B, 312B, 317B, 348B) were equipped with the AiResearch design. During the same time, UP equipped six A units (306, 310, 314, 315, 324, 336) and four B units (307B, 323B, 324B, 345B) with a competing design that was produced by the Elliott Co. of Jeannette, Pa.

A third design to be installed was EMD's turbocharger, which the builder had developed in response to UP's decision to turn to outside vendors to improve the performance of EMD locomotives. In March 1959, UP sent three units, in an A-B-A set (UP 301, 308B, and 305) to EMD's La Grange, Ill., plant, to be rebuilt to 2,000 horsepower, using EMD's then-new turbocharger. After being rebuilt, the locomotives were for all practical purposes pre-production GP20s, having been completed six months before the builder's 2,000-horsepower GP20 model was placed in production, since these three units contained all of the same features as the production GP20. Later, in May 1959, UP sent six more units, in two A-B-A sets (UP 300, 300B, 301B, 311, 313, and 320) to EMD to be rebuilt with the new turbocharger. These six units were not outfitted with GP20-style fuel tanks, air reservoirs, and walkway sideframe modifications.

Because of the success of the EMD turbocharger design on the nine units it modified in 1959, UP initiated a program in 1962, which continued until 1966, in which the railroad's Omaha, Neb., shops began retrofitting additional 300-class GP9 A units and B units with EMD's turbocharger. The railroad's own shop forces did the work by using parts furnished by EMD. By 1966, the railroad had installed EMD turbochargers in 27 of the 50 300-class A units, and in 27 of the 50 B units. At the same time, again because of the success of the EMD design, two other A units and six other B units that had been carrying AiResearch and Elliott turbochargers were retrofitted with the EMD design, bringing the total 2,000-horsepower GP9 fleet (known as Omaha GP20s) to 29 A units and 33 B units.

(click here for a separate article about Union Pacific's turbocharged GP9s.)

EMD F9A and F9B

In a continuing effort to upgrade older locomotives, in late 1958, UP contracted with EMD to modernize the road's fleet of 1500- and 1550- class F3s. The rebuilt units were to return to service on the Northwestern District numbered in the 500-class series, a slot that formerly had been occupied by the Oregon Short Line's 2-8-0 Consolidations. The last 500-class 2-8-0 steamers (533, 535, and 537) had been retired in March 1958.

The entire 500-series group of F9s (41 As and 43 Bs) was rebuilt from the remaining fleet of 84 F3s in both the 1500- and the 1550-classes, excluding four units involved in a November 1951 wreck at Orchard, Idaho, which were retired and rebuilt as F7s in 1952. EMD completely remanufactured the 84 units at its La Grange plant. The rebuilding work included replacing the 567B or BC engine with a 567C engine. All-new electrical gear was installed, including new D22 generators and new D47 traction motors. Both the railroad and EMD considered the units to be F9 locomotives, albeit in remanufactured F3 carbodies. The only external indication of the F9 internal components was the 48-inch dynamic brake fan on top and a rearrangement of the carbody side panels to the F9 configuration of a louver set forward of the forward porthole. The class was assigned to the Northwestern District, and the operating department tried to keep them from going either south of Ogden, Utah, or east of Pocatello, Idaho.

The carbody appearance of the 500s varied considerably from one unit to the next, because they were rebuilt from F3s that had been built in 1947, 1948, and 1949. The carbody styles were mixed due to the fact that there was no consecutive or sequential order to either the 1400-to-1500-series renumbering, or the 1500-to-500-series rebuilding. Because of this, the only accurate method to determine the carbody style exhibited by any particular 500-class unit is to examine a photograph of that unit.

GE 8,500-Horsepower Gas Turbines

Following the success of the 4,500-horsepower Standard and Veranda turbines, delivered in 1952-1954, UP in 1955 ordered additional gas-turbine locomotives from GE. Changing design features and developmental problems delayed their delivery until August 1958.

UP locomotives 1-30 were three-unit 8,500-horsepower Gas Turbine Electric (GTE) locomotives built in A-unit, B-unit, and tender configuration. The A units held the cab, all controls, and a Cooper-Bessemer FWB-6 850-horsepower diesel engine to power the auxiliary mechanical devices, and to act as motive power for short movements in yards and terminals. The B units held the gas turbine itself and four massive electric generators, which generated the power for the 12 traction motors, six each under each A unit and its corresponding B unit. The tenders were electrically heated (and some were insulated) and held 24,000 gallons of heavy residual ("Bunker C") fuel. They were rebuilt from steam-engine tenders that had once trailed 800-class 4-8-4s and 3800-class 4-6-6-4s. In 1964, UP raised the rated horsepower of the gas-turbines from 8,500 horsepower to 10,000 horsepower. (click here for more information about Bunker C fuel oil)

As with the smaller turbines, cost studies showed that UP had to keep these larger locomotives moving to extract the greatest cost benefit from them. However, increasing maintenance costs and a lack of reliability kept many of them in the shops. Also, the price of the Bunker C fuel on which the turbines depended as a major cost factor was increasing as the refineries found profitable uses for this residual fuel. By the mid-1960s, more and more of the units were spending time in dead lines. The first of the 8500 GTE locomotives was retired in August 1968, and others followed in 1969 and 1970. Most of the units retired in 1968 and 1969 were traded to General Electric, which used the turbines' three-axle trucks under the double-engined 5,000-horsepower U50C. The remainder, and the units retired in 1970, were sold to Continental Leasing, which scrapped the cab units, and stripped the turbine-generator sets from the B units for sale as stationary power plants. The units traded to GE also saw the same use for their turbines. One report stated that these components were used very successfully as stationary power plants on dredging barges constructed by Intercontinental Engineering, and that the actual turbines were the reason that the company had purchased the gas turbine locomotives.

Coal-Burning Turbine

Union Pacific's coal-burning turbine, a two-unit set with road numbers 80 and 80B, was built by the road's Omaha Shops over a more-than-two-year period, between September 1959 and December 1961. Stationary load testing took place at Omaha between December 1961 and mid-October 1962, with limited road trips taking place between Laramie and Rawlins, Wyo., on January 16 and April 7, 1962.

The control unit was rebuilt from UP Alco 2,000-horsepower PA-1 passenger unit number 607, which had been retired in March 1961 and sent to Omaha Shops for conversion (UP 607 wasn't actually renumbered to UP 80 until October 1962, when the rebuilt locomotive entered revenue service). Modifications to the Alco passenger unit included removal of the steam generator and main air reservoirs from the rear interior of the unit, and installation of an additional 3,852-gallon diesel fuel tank. The air reservoirs were re-installed along the roof.

The second part of the set, the turbine-containing unit, was built using the frame and running gear of Great Northern Railway W1-class electric locomotive 5018, which UP had purchased at scrap price from GN in September 1959. The turbine on the B unit were essentially the same as those on UP's road numbers 61-75 "Veranda" gas-turbines, with modifications to burn coal completed by Alco.

A tender for the set was rebuilt from the retired 14-wheel "Centipede" tender off a UP 3990-class 4-6-6-4 steam locomotive. It contained storage space for 61 tons of nugget coal, and equipment needed to crush and process the coal to a flour-like powder to allow the coal to be pumped as a fluid to the B unit for fuel.

The locomotive underwent modification and testing between January and October 1962, when it was placed in revenue service. On October 17, 1962, it made its first road trip between Omaha and Grand Island, Neb. It ran in revenue service from October 17 to November 15, operating between Omaha and North Platte, Neb., or Cheyenne, Wyo., accumulating a total of 3,000 miles. From November 16 to March 24, 1963, the locomotive was in Omaha Shops for further modifications and more stationary load testing. On March 25, it was placed back in revenue service between Omaha and North Platte or Cheyenne, accumulating 8,698 miles by July 1, 1963. It continued in service until May 12, 1964, when it made its last revenue trip, after which it was removed form service and stored.

The coal-burning turbine tests were unsuccessful because of excessive wear of the turbine blades caused by the fly ash from the coal, and also because of problems that surfaced in moving a dependable, continuous supply of pulverized coal from the tender to the turbine unit. After being stored in Council Bluffs, Iowa, the set was retired and never ran again.

UP 80 and 80B were renumbered to 8080 and 8080B in April 1964, at which time it was making its last runs, to avoid road-number conflicts with newly ordered DD35s. The B unit and tender were retired and scrapped by Omaha Shops during 1967. In March 1968, the A unit was retired and a month later, in April, was sent to EMD as trade-in on an order for new SD45s.


After EMD perfected its turbocharger in 1958, UP was one of the first roads to acquire the first locomotive model on which EMD mounted the device as standard equipment—the 2,400-horsepower SD24 design. EMD completed its first SD24 in July 1958, just after it had successfully completed tests on its turbocharged engine design. The first customers for the SD24 were Santa Fe and CB&Q, both in May 1959. Union Pacific's 30 SD24 units were delivered beginning in July 1959, numbered as 400-429. UP was the only road to purchase SD24 cabless booster units, which were delivered at the same time as the cab units. The booster units, of which there were 45, were numbered 400B-444B.

Following their delivery from June to September 1959, and for the following 10 years, UP's SD24s predominated as freight power over the road's South-Central District (the former Los Angeles & Salt Lake Railroad), between Salt Lake City and Los Angeles, through Las Vegas and southern Nevada. They usually operated in six- to eight-unit sets of two cab units with four to six booster units in between. Their delivery augmented the already existing large numbers of GP9s assigned to the district. The SD24s also allowed UP to eliminate the two major helper districts on the line, Cajon Pass and Cima Hill, both in California, with grades as steep as 2.2 percent.

In 1969 and 1970, with the arrival of 6900-series DDA40X Centennial units, UP reassigned the SD24s to the general motive power pool. But their unique low-speed pulling power was soon assigned, in 1971, in sets of eight (four cab units and four booster units), to U.S. Steel's Atlantic City (Wyo.) taconite iron-ore unit train that operated between the Atlantic City mine in central Wyoming and U.S. Steel's Geneva, Utah, steel mill. The units in Atlantic City taconite service were bumped in 1974 by UP's unique SD40X units. Others were assigned to switching service in large yards such as Los Angeles and Ogden, Utah, as well as to hump yards in Pocatello, Idaho, and North Platte, Neb. Several cab units were retired in 1977, and still more in 1980-1982. The last units, assigned to switch service, stayed in service until 1985. The cabless booster units were all retired in 1977-1981.


Union Pacific acquired 30 units of EMD's latest four-axle offering, the 2,000-horsepower turbocharged GP20 model, in July and August 1960. But the road was already familiar with the design because of its earlier tests with AiResearch and Elliott turbochargers and its collaboration with EMD on that builder's new turbocharger. UP retrofitted turbochargers on some of its GP9s in its Omaha Shops, and sent nine of its GP9s to EMD for retrofitting. After these units were modified, all of them became, in function and in specification, GP20s, but they retained their GP9 road numbers.

Formal GP20 production began in September 1959 (with six-axle SD24 production having started in May of that year). The first customer for the GP20 model was Western Pacific, in September. As noted, UP received its GP20s beginning in July 1960. As delivered, the 30 units were numbered 700-729. This series lasted for 2-1/2 years, until December 1962 and January 1963, when UP renumbered them in anticipation acquiring 35 newer GP30 units that were to be numbered in the 700 series, adjacent to the 800-series GP30s already on the railroad. UP renumbered its 30 production GP20s to 470-499.


In September 1961, Union Pacific purchased four former Alco RS-27 demonstrator units, built under Alco's DL-640 specification. Originally numbered as Alco 640-2 to 640-5 (Alco 640-1 was sold to Pennsylvania Railroad), these four units had been completed in December 1959 and January 1960, and were part of the total production of 26 units, built between 1958 and 1962. They were the first Alco units purchased by UP since the last PA passenger unit in January 1949, showing that UP had a long memory concerning the mechanical troubles of the earlier Alco units. Purchased at a bargain price (UP owned more former demonstrator units than any other road), UP numbered the units as UP 675-678, and the units were generally assigned to the Eastern District, usually on the Kansas Division between Denver and Kansas City. The first unit to leave the roster was 677 following a wreck on November 23, 1968 at Aikens, Kansas, which was also the cause for the retirement of U25B 627. The other three RS-27 units were retired in 1971 and sold for continued service on smaller mining railroads.

GE U25Bs

Following the break-up of a longstanding joint marketing and production consortium between Alco and GE in 1953, General Electric began design work on its first road locomotives. In September 1954, the builder completed a set of two cab units and two booster units, leasing it to the Erie Railroad from 1954 to 1959. While GE tested the design, the set ran in revenue service as Erie 750A and 750D (cab units) and 750B and 750C (booster units). In mid-1959, all four units were returned to GE for design improvements, and when completed, they carried the designation of model UM20B (U for Universal, M for Modified, 20 for 2,000 horsepower, and B for B-B trucks).

As built, all four units were equipped with Cooper-Bessemer diesel engines; the 750A and B carried 1,800-hp, 12-cylinder engines, while the 750C and D carried 1,200-hp, eight-cylinder engines. All four units were propelled by GE Model 752 traction motors. During their rebuilding in 1959, all four were equipped with 2,000-horsepower 12-cylinder Cooper-Bessemer engines.

Union Pacific purchased the four locomotives on October 21, 1959, numbering them 620, 620B, 621, and 621B. They remained in service for a brief four years, but during their early years, they proved that GE was indeed capable of building reliable diesel road locomotives (Apart from its joint work with Alco, GE's previous expertise in the locomotive field was limited to electric locomotives and very light diesel switchers). While these four units had been testing on Erie, GE had also undertaken a major redesign of the Cooper-Bessemer engine, completing its first 16-cylinder version in July 1958. In 1959, the builder completed two 2,400-horsepower prototype road-switcher units to further test its design concepts. These two units were originally built as export demonstrators (called XP24), but were changed to domestic units, designated U25Bs in 1960, and given GE numbers 751 and 752.

With the success of the XP24 prototype units, GE completed four of the later U25B design to serve as demonstrators. These were numbered GE 753-756, and later sold to St. Louis-San Francisco Railway. While they were in service as demonstrators, their brief stint on UP impressed the road, which soon placed an order for four units. Delivered in August 1961, they were the first U25Bs built after the demonstrator units. Given road numbers 625-628, these four units were equipped with high short hoods, as were a second group of four units, UP 629-632, that was delivered in May 1962.

After selling its first demonstrator set to Frisco, GE completed a second set in February 1962, numbered as GE 2501-2504. The builder in July 1962 sold these to UP, which numbered them 633-636. Three of the demonstrators also had high short hoods. GE 2501 (the later UP 633) was built with a low short hood, a design similar to the low noses EMD had furnished earlier to UP on new GP20s and SD24s. In August 1962, GE delivered four more low-nose units to UP (numbered 637-640), raising the road's U25B fleet size to 16 units.

All 16 units were used systemwide in general pool service for about 10 years. By the late 1960s, the U25Bs were among the first units to be stored every time there was a traffic downturn, and in September 1972, barely 10 years after they gained the distinction of being the first U25Bs to be built, they were the first U25Bs to be retired. In 1968, UP assigned units 633, 638, 639, and 640 to hump service at Pocatello, Idaho, replacing retired Baldwin AS-616 units. UP 632 was rebuilt with a 12-cylinder engine in April 1969, testing the design that would be installed later that same year in new U50Cs.

EMD GP30s and GP30Bs

After testing the GP22 (later changed to GP30) prototype unit, EMD 5629, in 1961, Union Pacific ordered 75 production versions to be numbered as 800-874. This first group of production GP30s was delivered in July and August 1962. The GP22 prototype was rebuilt as the GP30 demonstrator, and UP purchased this unit in September 1962, renumbering it 875. Thirty-five more GP30s were delivered in February and March 1963 as UP 700-734, with a single additional unit, UP 735, delivered in June 1963 (built with a wrecked F9 as a direct trade-in). As with the earlier SD24s, Union Pacific ordered cabless booster versions of the GP30 model. These unique-to-UP locomotives were delivered as units 700B-739B from April through July of 1963. The last 13 of them, numbers 727B-739B, were delivered equipped with steam generators for use as standby passenger units, and for service on special movements such as mail and express trains, and on the movement of circus trains visiting cities along UP's route.

For the first seven to eight years, the GP30s were used on the road's priority trains, operating between its eastern terminals and terminals on the west coast. With the arrival of six-axle high-horsepower SD40s in 1966, some GP30s were bumped down for regular assignment on some of the road's secondary freights. With the SD40s themselves bumped down to secondary service after the delivery of DDA40X Centennial units and SD40-2s, many of the GP30s entered branch line and local service, and some became switchers in the larger yards.

Spokane International Alco RS-1s

In 1962 Union Pacific leased the 12 Spokane International Alco RS-1 locomotives, built as Spokane International Railway 200-211 in 1949 and 1953. On October 6, 1958, Union Pacific purchased 99 percent ownership of Spokane International. The road continued to operate between Spokane, Washington and its connection with Canadian Pacific using the original locomotives. In 1962 the operations were changed to use more powerful Union Pacific locomotives and the 12 SI units were leased to Union Pacific. UP repainted them to UP's standard yellow and gray paint scheme, with Spokane International spelled out in UP's rounded Gothic style lettering. The RS-1s were moved by UP to its Eastern District and were assigned to Denver and La Salle, Colorado during 1962 and Kansas City during 1967.

An example of the units' early assignment was on a day in December 1962, when the dispatcher's sheets show that SI 1214 and 1216 were both working on the "LaSalle Switcher" that day. Switchers based out of LaSalle, Colorado worked the various northern Colorado branches and customers along the mainline.

EMD DD35, ALCO C-855, and GE U50 Double Diesels

In its search for its ideal three-unit 15,000-horsepower locomotive, Union Pacific in 1963 purchased EMD's DD35s, GE's U50s, and Alco's C855s, all of which were delivered in 1964 and 1965. These were the first of UP's trademark "double diesels." While all three designs met the requirements of the conceptual design, the reliability of the GEs was disappointing, and that of the Alco units was even more so. Having just entered the road-locomotive market on its own two years earlier, General Electric was eager to build reliable units, and its post-sale customer service reflected that, with much time being spent fixing the U50's reliability problems. The three designs were a direct result of studies by the road's own mechanical staff during 1962, which had shown that bigger was better. These studies showed that no matter how large or small a locomotive's horsepower rating was, the annual per-unit maintenance cost was $7,000. Having developed this bit of data, Union Pacific decided that to meet its future motive power needs, it would purchase large-unit, high-horsepower locomotives.

The first examples of General Electric's offering, the U50, were delivered in October 1963 as UP 31, 32, and 33. These units, along with the Alco units delivered in June 1964, as UP 60, 60B, and 61, rode on the twin two-axle span bolster trucks from retired Standard and Veranda 4500 GTE locomotives. The reliability of the Alco units was unsatisfactory, but more GE U50s were delivered in from July through September of 1964 (12 units, UP 34-45), and again from May to August of 1965 (eight units, UP 46-53), making a total of 23 5,000-horsepower GE units.

EMD delivered 25 DD35 cabless booster units from May through September of 1964, numbered 74B-98B. EMD had built two original DD35 demonstrator units in September 1963, along with two accompanying GP35 cab units, and sent this GP35-DD35-DD35-GP35 15,000-horsepower set to several other roads to demonstrate the concept of large, high-horsepower locomotives. UP purchased the demonstrators in May 1964 along with the first of its 25-unit production order.

When UP had asked the three builders in 1963 to build these three designs, the road had suggested the span-bolster style of suspension that GE and Alco ultimately used on their units. EMD chose to furnish its units on an all-new, four-axle design—D-D trucks, using the AAR designation for four powered axles. UP was so pleased with its 27 DD35 units that it ordered 15 more of them, but equipped as cab units; they were delivered from April to June 1965 and numbered 70-84. The first 14 of these units were unusual in that they were powered by GE traction motors from trade-in Alco FA/FB units that UP had purchased in 1947-1948. The fifteenth unit, UP 84, was equipped with the traction motors of wrecked trade-in GP9 159.

All of these double-diesel units were used systemwide during their early years of service. The Alco units were the first to be removed from service, after being restricted to the Eastern District soon after being built. They were retired in 1970, just six years after delivery. The GE units also tended to stay on the eastern end of the system, but were used regularly on trains all over the system. It was the 42 EMD units that were able to work on any train the road wanted them for, and they continued in mainline service for over 15 years, being retired in 1979 and 1980.

One of the most noticeable features of these EMD units in their later years was the addition of external sand boxes. Of necessity, when these units were built, their electrical cabinets were located at the ends, as were the sand boxes. As the units aged, the sand boxes began developing minute fatigue cracks that allowed very fine and gritty dust to enter the electrical components, causing excessive wear and electrical problems. To combat this dust problem, UP began relocating the sand boxes to the units' walkways, using a design very similar to that used on the DDA40X Centennial units.

(click here for a separate article about Union Pacific's DD35s.)


Of the 24 GP35s delivered to Union Pacific in 1964, two were notable as the first two of total production of over 1,300 GP35s. Intended as an improved GP30 (with its 2,250 horsepower), the 2,500-horsepower GP35, with its features that included easier maintainability, was introduced to the nation's railroads in September 1963 as part of a massive 15,000 locomotive set that included two GP35s (which became UP 762 and 763) and two 5,000-horsepower DD35 booster units (which became UP 72B and 73B). The set, painted in a striking orange and white paint scheme, toured the country, but only UP and SP bought the double-engined booster units. Other roads saw the potential of the single 2,500-horsepower unit and eventually 1,333 units were sold to U. S., Canadian, and Mexican railroads, with the GP35 remaining in production until December 1965, when it was replaced in EMD's catalog by the 3,000-horsepower GP40. UP purchased its two former demonstrator GP35 units in May 1964, along with the two DD35 units, after the four units had completed their nationwide tour. The follow-on order for 22 additional GP35s were delivered in May and June 1964 and saw service system wide. Although the demonstration set operated in its initial GP35-DD35-DD35-GP35 configuration, and as dramatic as the set may have appeared to interested observers, the reality of day-to-day operation seldom saw a similar consist of locomotives in normal road service. By late 1982, only four of the original 24 units had been retired. The other 20 units were active and many were being used in either local service or were in switch service at many of the road's smaller terminals where the added flexibility of road units were needed instead of dedicated switcher designs.


The 10 SDP35s UP acquired in 1965 were intended for passenger service (they were purchased just 18 months after the newest E9s), and later exhibited the same electrical problems that were common to all of EMD's 35-line locomotives. UP assigned its SDP35s to the Eastern District (Nebraska and Kansas Divisions), keeping them close to Omaha for use in special passenger moves. UP's SDP35s were used, along with steam-generator equipped GP30Bs, on Vietnam-era troop trains. These troop trains operated between Fort Riley, Kansas, and the West Coast. Three SDP35s were used at least once on the "Snowball Express" ski trains between Salt Lake City and Park City, Utah, located in the high Wasatch Mountains of northern Utah. In later years, the SDP35s were assigned to pilot duty between Fremont and North Platte, Neb., providing UP radios and Coded Cab Signal equipment on run-through Chicago & North Western trains. With the availability of six GP40X units for use on special moves, beginning in mid-1980, the SDP35s were stored, along with hundreds of other examples of UP motive power, due to a downturn in the national economy. They remained in storage until their retirement and sale in 1985.


After taking delivery of high-horsepower double-engined locomotives during the 1963-1965 period, Union Pacific was ready to upgrade other units in its fleet. The road was operating several run-through trains that pooled motive power with other railroads. In 1966, in part to support its pool-power agreements, UP bought off-the-shelf examples of locomotives from all three builders, Electro-Motive, General Electric, and Alco, in the form of EMD's SD40s, GE's U28Cs, and Alco's C-630. Given the costs of owning more units, and confirming previous experience with EMD designs, UP found that the SD40 model was much less costly to both operate and maintain, and placed a follow-on order that brought the SD40 fleet size up to a total of 83 units, while the 10-unit fleets of U28Cs and C-630s remained as orphans—that is, solitary examples of those models on UP. EMD's SD40 employed the builder's newest technology—the 645 model diesel engine, the AR10 alternator, and the D77 traction motor—and UP soon came to appreciate the reduced costs of owning and operating this six-axle, 3,000-horsepower unit over the those of the builder's previous combination of a 567 model engine and DC generator.

UP's first 40 SD40s, numbered 3000-3039, were delivered in March and April 1966. Alco's C-630s were delivered in May and October 1966, and the GE U28Cs were delivered in June and August 1966. More SD40s arrived from October to December 1966, numbered 3048-3082.

After UP acquired its first 83 SD40s in 1966, the road bought SD45s in 1968, and double-engined DDA40Xs and U50Cs in 1969-1971. These high-horsepower units were intended to operate over most of UP's system, from the North Platte terminal in the east to the West Coast terminals. By early 1971, UP was seeing an increasing number of run-through trains with connecting carriers, all of which included agreements for run-through motive power. UP's double-diesel, high-horsepower units were unwelcome on these other roads, so to keep a reliable fleet of power that could be used acceptably on run-through trains, the road returned to EMD for 40 more six-axle, 3,000-horsepower SD40 units. Numbered 3083-3122, they were delivered from August to October 1971, bringing the railroad's SD40 fleet size to 123 units. UP ordered 50 more SD40s for 1972 delivery, but with EMD's change to its "Dash 2" line in January 1972, these were delivered as SD40-2s, numbered 3123-3172.

EMD SD40 Demonstrators

After announcing its "40-Line" in June 1965, EMD completed nine combination test and demonstration units, using its then-new 645-cubic-inch-per-cylinder diesel engine and then-new AR10 alternator, mounted on the frame of the builder's production SD35 locomotive. The first unit, EMD 434, was painted first in EMD demonstrator colors, then in Santa Fe-like blue and yellow. It was later sold to Gulf, Mobile & Ohio and numbered 950 on that road. EMD completed eight others and numbered them 434A to 434H, painting them in an all-black scheme, from which stemmed their "Black Bird" nickname. Known as either SD40Xs or as SDX40s, depending on the source, the units operated in test and demonstration service on several roads, including in Mexico and Canada, before EMD sold them to Union Pacific in February 1966 as UP 3040-3047. In mid-February 1966, 434C and 434D were sent to demonstrate in Canada (as CP 7001 and 7000, respectively), and then to Mexico in March. Six units (434A-B and 434E-H) were delivered to UP immediately, arriving two months before the road's first 40 regular-production SD40s, road numbers 3000-3039. The remaining two units (434C and 434D) were delivered to UP in April 1966 after their tours of Canada and Mexico. Later research has shown that EMD's own electrical schematics has these unique units labeled as SD40X.

The carbodies of units 3040-3045 (six units) had flared radiator sections, similar to those of production SD45s, but shorter. UP 3046 and 3047 had flat radiator sections, like those of production SD35s and SD40s, and were similar in appearance to SD35s, except for having three rooftop 48-inch radiator fans instead of two 48-inch fans bracketing a single 36-inch fan.

Because of their different electrical systems, UP usually kept these eight units together. In January 1974, UP assigned them briefly to potash trains at Soda Springs, Idaho. Within a month, the road reassigned them to the taconite unit ore trains between a mine in Wyoming and the U.S. Steel Corp. steel mill at Geneva, Utah, replacing eight unit sets of SD24s and SD24Bs which had been assigned to that particular service since 1971. In late 1975, UP equipped all eight units with Pacesetter speed control and transferred them to heavy switching and hump yard service in North Platte, Neb., and Kansas City, Kansas. Although they were equipped for slow speed heavy switching after 1975, the units were still not limited to yard duties. At times individual units would be assigned to road service as required, and continued to be seen at many locations until the mid 1980s. As examples: UP 3042 was seen in Seattle in March 1977, and 3040 was at Seattle in June 1979. After that time, and until their retirement, or lease to Mexico in 1989, they were used almost solely in heavy switching at North Platte.

Canceled SD40 Order

In early 1967, UP ordered five additional SD40 units. At EMD , they were assigned builder's numbers 32435-32439, and were to carry UP road numbers 3083-3087. UP canceled the order before they were built. The builder's numbers were never used again by EMD for any other units.


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