EMD GP35

The EMD GP35 emerged in 1963 as General Motors Electro-Motive Division's entry into the 2,500 horsepower road switcher market, a segment where competition among locomotive builders was intensifying during the early 1960s. Production began in July 1963 and continued through December 1965 at EMD's La Grange, Illinois facility, while General Motors Diesel, EMD's Canadian manufacturing arm, produced additional units between May 1964 and January 1966. When final tallies were complete, 1,251 locomotives had been delivered to American railroads, with an additional 26 going to Canadian buyers and 57 destined for service in Mexico, bringing the total production figure to approximately 1,333 units across the model's run. The GP35 arrived at a particularly advantageous moment for locomotive trading programs, as many railroads were actively retiring first-generation cab units and seeking modern replacements. Numerous roads traded in Alco FA units and EMD F-units as partial payment toward their GP35 orders, and in an economical practice common to the era, builders sometimes reused the trucks and traction motors from the traded locomotives in the new units. This resulted in a notable subset of GP35s riding on Alco-pattern trucks, with examples operated by the Gulf, Mobile and Ohio, Southern Railway, and Ann Arbor Railroad among those so equipped. The GP35 occupies an important place in EMD's product lineage as a transitional design bridging the early turbocharged road switchers and the highly successful GP40 that would follow. Though its production run was relatively brief, the model served a wide variety of railroads across North America and proved durable enough that examples remained in active service with some operators for decades. Several preserved examples survive today at museums and tourist railroads, representing the breadth of railroads that once relied on the type.

The GP35 was powered by a sixteen-cylinder turbocharged version of EMD's long-running 567 prime mover, designated the 567D3A, which produced 2,500 horsepower and drove the locomotive's four traction motors through a direct current electrical transmission. The locomotive rode on a B-B wheel arrangement, meaning two two-axle trucks, each axle independently powered, a configuration that balanced tractive effort with axle loading and made the type suitable for a wide range of mainline and branch line assignments. The use of turbocharging on the 567 series engine allowed EMD to extract significantly more output from the established powerplant without a wholesale redesign, though the 567D3A represented a refined iteration of the turbocharged 567 technology that the builder had been developing through previous models. The GP35's electrical systems used direct current throughout, consistent with EMD practice of the period before the transition to alternating current main generators that would characterize later designs. The reuse of trucks and traction motors from traded-in predecessor locomotives on a portion of the production run introduced some variation in the mechanical configuration of GP35s across different railroads, with Alco High Adhesion trucks appearing under certain units in place of EMD's standard Blomberg B trucks. This fleet-level variability was an accepted consequence of the trade-in economics that made the model attractive to budget-conscious railroad mechanical departments during the mid-1960s transition away from first-generation motive power.

Models by: Broadway Limited · Kato · Walthers