Union Pacific's Final Four

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UP's Last Four SD40-2s

This page was last updated on January 1, 2016.

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Union Pacific SD40-2s 3805-3808 were different from the hundreds of other SD40s operated by UP. After much discussion among certain diehard UP diesel researchers, with some input from both current and former EMD and UP employees who were there, here is the story...

In November 1980, Union Pacific accepted delivery of four special SD40-2 locomotives from their builder, Electro Motive Division of General Motors. These four locomotives were part of test by UP and EMD for the builder to build an improved SD40-2 for UP. UP 3805-3808 were originally part of EMD order 796345 for 40 units to be numbered as UP 3769-3808, but were changed before their construction to become a special four-unit separate order, 806053.

All four units were initially equipped with improved engines that had strengthened engine blocks and improved turbochargers, and were rated at 3,300 horsepower. The increased horsepower came from adjusting the engine governor.

They were equipped with EMD's standard D77 traction motors, not the later D77B or D77X3B motors that were installed on UP's 6900 series DDA40X units.

These four units had larger radiators (an extra standard radiator core, at 27-1/2 inches long) and two-speed radiator fans.

The tests lasted only one year, after which all four units were returned, at EMD's expense, to standard SD40-2 configuration, except for the extra length in their carbodies. A retired test engineer at UP told researchers that since EMD paid for the test program, UP does not have any mechanical department records, other than correspondence between EMD and UP setting up the special one-year test.

The units' carbodies are longer than a standard SD40-2, to accommodate the longer radiators; the long-hood end was fitted with eight doors under radiator section, rather than seven, and a shorter rear platform. (To produce the Overland HO scale model, Tom Marsh measured one of the units at Jenks Shop in North Little Rock, and found an additional 28 inches in carbody length.)

EMD used SD40-2S, for SD40-2 "Special" as the model designation on internal engineering documents; UP's designation was SD40-2.

At the end of the one-year test, and like the previous SD40-2s before them, UP 3805-3808 were later equipped with EMD's 645E3B engine. Comments about them being equipped with "strengthened" engines indicates that these four units were EMD's test of what would later become its 645F engine, which included a improved crankcase and better oil circulation for better engine cooling, as well as a stronger upper engine block. Although the EMD 645F only designates an improved crankcase, the same improved upper engine block was introduced on the SD50/60 series and is usually referred to as the "heavy block." The same heavy block engine is today the standard replacement for all EMD 645 engines.

During the one-year test, the four UP locomotives were also equipped with an improved turbochargers and improved intercoolers, which increased air flow and cooling to the engines themselves. These features were later included in EMD's SD50 and SD60 locomotives.

Wiring diagrams for the four locomotives, examined during late 2000, show that the four units retained the two-speed radiator fans from the one-year test period. Two-speed radiator fans were formally introduced by EMD on its SD50 locomotives and were an innovation at the time. Two-speed fans were supposed to save a little fuel, save wear and tear on the fans, and help maintain a more stable water temperature.

Not Super Series

Contrary to previously published reports, these four units were *not* equipped with EMD's "Super Series" wheelslip control. During a period of research from June through November 2000, looking for applicable documents among the records in Union Pacific's mechanical department, no mention was found of these four units being unique in any way.

As background, EMD's Super Series was introduced in June 1975 on two Clinchfield SD45s, 3619 and 3621. By late 1977 EMD formerly introduced Super Series locomotives with the test bed SD45X units, and on the six GP40X units for UP, numbered as UP 9000-9005. In April 1978, EMD built four SD40-2 locomotives for BN, numbered as BN 7049-7053, as the first production six-axle locomotives to have the Super Series installed. These four units, built under EMD order number 776083, had all six traction motors wired in parallel, which required the new higher output AR16 alternator, and used conventional SD40-2 car bodies. In September 1979, EMD built four SD40X locomotives for KCS, numbered as KCS 700-703. These four KCS locomotives were essentially an SD50 carbody on an SD40-2 frame, and had 3500 horsepower with the Super Series wheel control system, and were equipped with the larger AR16 alternator. In December 1980, EMD built six SD50S units for N&W, numbered as N&W 6500-6505. These four N&W units were equipped with 3500 horsepower, AR16 alternators, and Super Series wheel control, with a near exact SD50 car body on a SD40-2 frame.

Purpose Of Test

Back to UP's four SD40-2S units: This test may have been the precursor to an order UP had for an additional 120 SD40-2's (3809-3928) for delivery in the first three quarters of 1981. Eighty of these were cancelled in early 1981; the remaining 40 were cancelled in June 1981.

EMD built the first SD50 locomotives in December 1980. UP tested two new N&W SD50S-designated models (N&W 6500 and 6501) in April 1981, but with over 600 units in storage by late 1982, UP waited to buy the new model until 1984.

Research has not yet found how these four units for UP relate to the SD40X locomotives built for KCS in 1975, or the SD50S locomotives built for N&W in late 1980, or the special SD40-2s built for BN in 1978. As a visual indicator, the KCS SD50S units had the newer angled blower ducts as used on production SD50 units, along with two speed radiator fans and wheel slip control. The shop superintendent at BN's Alliance, Nebraska, shops informed researchers that the BN units had the strengthened engine blocks but apparently did not have the two speed radiator fans.

There were supposedly some labor problems at EMD's La Grange plant when these UP and BN units were built, so any EMD records concerning this apparent test program were tied up in that legal effort.

The 1986 EMD Product Reference book, which supposedly shows all EMD locomotives in service at the time, shows UP 3805-3808 as order number 806053 and wiring diagram WD01190, compared to UP 3769-3804 with order number 796345 and wiring diagram WD01050. After being examined by a UP employee, the only difference in wiring diagrams was found to be the two-speed fans, with no mention of wheel slip controls or anything else not on the other 36 units in the original group (UP 3769-3808).

The UP locomotive diagram book shows UP 3769-3808 on the same page, right from the initial date of May 1980 (Sheet L-56-13, original date of 5-29-80). Later revisions ( Rev. C, 1-85, Rev. D, 6-85, Rev. E, 12-86, and Rev. F, 9-94) make no mention of anything different among any of the 40 units in the last group.

The following comes from a source within UP's operating department, via an email dated November 13, 2000:

In late August, I inspected UP 3808, and have since had a chance to inspect UP 3804 and 3807. The only two items separating these units from any of the other SD40-2's are the 2-speed cooling fans and the longer radiator cores. These locomotives have an extra 27 1/2" radiator core segment on each side. The cores are not taller or thicker than standard SD40-2 cores. In fact, the extra segment is just a standard SD40-2 single-length core segment.

As information, radiator cores are manufactured in segments, which are noted by length. These segments can be bolted together to achieve the desired length. EMD and outside vendors make these generally in 27 1/2" and 55" lengths. Radiator cooling capacity depends on a number of factors that affect the amount of surface area for heat exchange. Thus, the length, height and thickness of the cores is controlling. In most cases, adding a segment or two to the basic core is how EMD added cooling capacity, along with the capacity and the number of fans. Thus, the only difference between the cooling system on a GP38-2 and an on an SD40-2 is the number of radiator segments and fans. The fans and the segments are the same on each; the 40-2 has 1 more fan and 2 more segments (one on each side) than the 38-2.

(More cooling capacity in the radiators means the fans don't have to work as often or as hard, which is a fuel-saving thing).

The EMD parts books still show the SD40-2SS as a specific model (for Super Series wheel slip-equipped units). I've been unable to find any specific parts for an SD40-2SS except for the main alternator. Along that line, I can't find anything that says UP 3804-3808 were delivered as anything other than SD40-2's with a different cooling system. The wiring diagrams do not show any kind of odd wheelslip system ever having been aboard these units, nor do they show an odd alternator ever having been on them, either.

EMD would have given an improved or modified engine a different designation. They would have to, in order to keep track of it and prevent mismatched parts, such as the case and pan. Personally, I suspect that if the engines were, in fact, rated at 3,300 hp, the only difference would have been the governor, but I also think these things would have run hot all the time. Otherwise, "strengthened" blocks would have required a new designation, say, 645F (which was used later) or 645E4, or 645E3C or 645E7 (the marine version of the 645) or 645D or even 645G.

Current Status

UP 3805 Nov 1980 806053-1 29 Nov 2001     1
UP 3806 Nov 1980 806053-2   UP 3412 (2nd) 3 Nov 2003 2
UP 3807 Nov 1980 806053-3   UP 3277 (2nd) 23 Jun 2004 3
UP 3808 Nov 1980 806053-4 30 Jan 2002     4


  1. UP 3805 was retired by UP and sold to GE for lease to Iowa, Chicago & Eastern (ICE) 6406 in January 2003; ICE merged along with Dakota, Minnesota & Eastern Railroad into Canadian Pacific in September 2008.
  2. UP 3806 was renumbered to UP 3412 (2nd) in November 2003 to clear the 3800 series for use by new SD70M units; renumbered to UP 1924 in November 2014; rebuilt to UPY SD40N 3005 in June 2015 and paired with yard slug UPY 3006.
  3. UP 3807 was renumbered to UP 3277 (2nd) in June 2004 to clear the 3800 series for use by new SD70M units; still in service as of October 2013.
  4. UP 3808 was sold to Evansville & Western (EVWR) 6003 by March 2006


Sources include correspondence during June through November 2000 between Don Strack, Bill Metzger, George Poindexter, and other indiviuduals who were employees of Union Pacific, and who prefer to remain unnamed.

Original version first published to LocoNotes Yahoo group on November 12, 2000.