Bio Edit

The EMD (Electro Motive Division) GP40X is a type of four-axle, 16-cylinder, 3,500hp diesel locomotive built from 1977 to 1978.
UP GP40X units

UP #9000 leading four of its brethren sometime in the early-1980's.

It is a rare, experimental variant of the GP40 or GP40-2 (the "X" meaning, "experimental" or "xperimental"), with only 23 built and only half still remaining on various leasing, shortline, and industrial companies, while several are currently in service with BNSF.

Three ex-UP units (including one ex-SP unit) have since been sold and rebuilt into what are essentially GP38-2's for CP (Canadian Pacific): having been rebuilt to GP38-2 specs, while still retaining its distinct appearance. Said units are numbered CP 4521-4524).

Southern Pacific (SP), Santa Fe (ATSF), Union Pacific (UP), and the Southern Railroad (SOU) were the only customers to receive orders for the model, and were delivered in response to evaluation and field testing under EMD.

History Edit

The GP40X was an experimental model of four-axle diesel locomotive, which was part of EMD's development to increase the efficiency of their prime-movers to obtain more horsepower or to attain the highest horsepower output possible with their existing 645 engine line; as well as introducing new technology into their range of diesel locomotive models, furthermore attempting to get ahead of the competition from GE. Having introduced the latest variant or version of the 645 series prime-mover or engine: the 16-645F3 (or 16-645F), the engine served as a milestone for four-axle or four-motor diesels by including an increased (yet over-stressed) rpm via an improved alternator: the AR10X2 (which eventually became the AR15), and the latest traction motor model: D87X (later D87) to help boost the usual horsepower rating of 3,000 or 3,200hp from the existing 16-645E3, to 3,500hp or 3,600hp. Although only a mere 500hp difference, the 645F3 engine model proved to provide a more efficient amount of tractive effort over the preceding GP40-2 and subsequent GP40; despite having proved to be plagued with issues once production began.

UP #957 (originally UP #9003, later UP #93) revealing its optional, experimental HT-B trucks. The unit is now CP #4522, and is currently dubbed as a "GP38-2": having been rebuilt to GP38-2 specs.

Having been equipped with some of the earliest known computer microprocessor modules and controls which foreshadowed the succeeding GP50 (and future models), the GP40X served as a prototype, testbed, or demonstrator for the latter. Such included features were digital speedometers which indicated speed under a roof-mounted doppler-radar gun utilized for measuring speed and detecting speed limits, as well as including the earliest known form of the revolutionary "Super Series" wheelslip control system present on today's current EMD models. Other features consisted of automatic fuel starters, an improved split-cooling system consisting of larger air intakes to help improve the temperature conditions of the engine compartment interior (though, the air intakes or radiators were flared like with the SD45 as opposed to being non-flared like its successor), as well as having an early form of distributed power (DPU) integrated, known as "locotrol": which involved the ability for multiple sets of locomotives within a train to be controlled simultaneously at the same consistent speed from the lead unit via a remote-control radio frequency system without the need of crew members activating or starting other unit's motors or engines manually ("on the fly"), or requiring manned sets of helpers (which proved to be effective for western carriers like SP and ATSF, with the exception of SOU).

Despite its initial success, only two of the original owners whom originally demonstrated the model placed orders for the succeeding GP50 once production was underway: Southern (SOU) and Santa Fe (ATSF), for the GP50 failed to garner the same amount of success as its predecessors.

EMD 433AEdit

The "GP40X" designation was also given to EMD 433A: a testbed built on a modified GP35 frame which was one of the earliest known diesels to be equipped or fitted with a 645-series engine, and served as a precursor to the GP40. The unit was eventually sold to the Illinois Central (IC) and became IC #3075. The unit was eventually rebuilt into a GP35 (ICG #2550) in 1974 after an involvement in a wreck before suffering its final fate.

EMD 433A

EMD #433A: the unique testbed built in 1965.

The 1965-1966 EMD 433A has very little in common with the 1977 GP40X other than flared radiators and a 645-series prime mover, though both models are vaguely similar in appearance.

Ironically, both models share the same identity crisis or dilemma as the SD40X testbeds for the original SD40 and the SD40X for the subsequent SD50. Even more ironic, is how rival GE utilized the same name for two completely different locomotive lines, but shared the same concept: being an improvement over the preceding models.


Model GP40X GP50
Production Dates 1977 to 1978 1980 to 1985
Total built 23 278
Length 60' 2" 60' 2"
Wheel arrangement B-B B-B
Engine (prime-mover) 16-645F3 16-645F3B
Horsepower 3,500 3,500
Alternator AR10X2-D14 AR15-D18
Traction Motors D87X D87
Weight x 1,000 lbs. 274-278 260-277

Production RosterEdit

Owner Quantity Road Numbers Truck Type Notes
Atchison, Topeka, And Santa Fe (ATSF; Santa Fe) 10 3800-3809 Blomberg M

3800 Locotrol Master

3801 Locotrol Receiver

Southern Pacific (SP) 2 7200-7201 HT-B Locotrol Receivers; Delivered with "Elephant ear" intake screens
Southern Pacific (SP) 2 7230-7231 HT-B Locotrol Receivers; Delivered with "Elephant ear" intake screens
Southern Railway (SOU) 3 7000-7002 Blomberg M Built with "hi-hood" (high-short hood or high-hood)
Union Pacific (UP) 6 9000-9005 HT-B Renumbered multiple times before retirement


Ironically, during the UP-SP merger in 1996, UP received SP #7231: the sole-surviving GP40X used by the original owner that wasn't sold to a leasing company prior to the merger. Renumbered UP #9999, the unit had a very short-lived career on the railroad, and was used as a spare alongside fleets of aged GE Dash 7 units in case a power shortage were ever to occur. It was eventually retired and sold to National Railway Equipment (NRE) by 2003-2004, and was rebuilt into a GP38-2 for CP (CP #4521). The #9999 number has also been given to an AC4400CW  and SD40-2, yet the number is only a temporary designation.

"Elephant ears" (air shields or air intake deflectors) were fitted to the SP GP40X units as an experiment to draw cooler air into the radiators more effectively and efficiently, similar to the earlier experiments with some SD45's, SD40-2's, and subsequent SD40T-2's and SD45T-2's. They were eventually removed, for they proved to be unnecessary.

The HT-B truck was also originally available as an option with the GP50 during production, but never received orders.

The Toledo, Peoria, and Western (TPW) shortline owned by RailAmerica (now G&W) owns a former SP GP40X which still retains its original trucks, and is also an example of a surviving GP40X.

The ATSF's fleet of GP40X units were the only units delivered without any special features.

Like many other units employed by SP during the 1970's-1980's, their GP40X units were built with L-shaped driver's-side windshields before they were eventually reverted back to the standard four-piece windshield present on all standard or conventional-cab EMD diesels.

Like every other EMD diesel locomotive purchased by the Southern Railroad other than the GP59, the GP40X had a "hi-hood" variant built specially for the railroad for LHF ("long-hood forward") operations.