(either a sprag-operated transfer case Rockwell 136-21 or air-operated selectable transfer case Rockwell 136–27). Multifuel engines are designed to operate reliably on a wide variety of fuels, including diesel fuel, kerosene, heating oil or gasoline. Gasoline may be used only in an emergency because it does not properly lubricate the injector pump. While using gasoline, common practice calls for the addition of at least 1 U.S. quart of clean motor oil per 15 U.S. gallons of gasoline (1 imp qt/13 imp gal; 1 L/60 L) for proper pump lubrication where available. Although the A2 version is the most common, there are four different iterations: Standard, A1, A2, and A3. These changes mainly had to do with the engine and transmission components. Standard M35 had a REO "Gold Comet" or Continental OA331 inline-6 gasoline engine. Some had 4-speed transmissions but most had "direct 5th" transmissions. The gasoline-powered deuces were built primarily by REO Motors, however, Studebaker also had a manufacturing contract from at least 1951 into the early 1960s. Curtis-Wright also had a contract in at least 1958 to build dump trucks with the Continental gas engine. The A1's had Continental LDS-427-2 turbo engines, equipped with either a model 4-450 Schwitzer turbo or a 4D454C Schwitzer turbo on later models, and 5th gear was an overdrive. The 140 hp engines were not reliable, suffering frequent headgasket failures. The first A2 trucks received the bigger LD-465-1 naturally aspirated 478 CID multifuel engines, keeping the OD transmission of the A1s. Through the years the trucks were upgraded to LD 465-1c engines, with 60Amp alternator instead of the 25Amp generator. With the addition of a turbocharger, the engine evolved into the LDT 465-1c (turbo clean air). The turbo was added more to clean up the black exhaust on the Non Turbo engines, than to add power; the HP was raised from 130 to only 135 HP. Turbo models used: 3LD305 (early engines only) and 3LJ319 (the "whistler") The LDT-465-1D was the last version of the Multi Fuel, it had the same 3LJ319 Turbo (whistler), or the quieter 3LM39 (non-whistler), better head gasket sealing and head cooling. M35A3 From 1994 until 1999, the M35A3 variant was introduced as part of Extended Service Program. Usually, A3 vehicles have a Caterpillar 3116 Diesel engine and had their manual transmissions replaced with Allison 1545 4-speed automatic transmissions, as well as receiving numerous other improvements with a redesigned frontal