US-6

Engine and driveline

Hercules JXD engine

Dump truck w/winch shift patterns

Long wheelbase frame

The US6 used a Hercules JXD engine, with an 320 cu in（5.2 L） L-head inline 6 cylinder gasoline engine developing 86 hp（64 kW） at 2800 rpm and 200 lbf·ft（271 N·m） of torque at 1150 rpm. A conservative-type and highly-reliable engine with a compression ratio of only 5.82:1, it could use 72-octane gasoline. This same engine was also used in the M3 half-tracks and, later, M8 Greyhound and M20 armoured cars (the latter was a variant (lacking the gun turret) of the M8 Greyhound).[5][2][3][6]

The Warner T 93 5 speed transmission had a very low first, a direct fourth and an overdrive fifth gear. A power take-off could be fitted to operate a winch (mounted just below in front of the radiator) and/or the hydraulic hoist on dump trucks (the U10/U11 and U12/U13 dump truck models).[7]

The Timken T-79 transfer case had high and low ranges, a neutral position and could either engage or disengage the front axle. There was one output shaft mounted forward to the front axle (not used in 6x4 trucks) and two to the rear, with one for each rear axle.[8]

Both front and rear axles were of the Timken split-type with a ratio of 6.6:1. The front axle had ball-type constant-velocity joints while the two at the rear were full-floating.[9]

Chassis

The US6 had a ladder frame with three beam axles, the front on semi elliptical leaf springs, the rear tandem on quarter elliptical leaf springs with locating arms.[10][11]

There were two wheelbases, the short 148英寸（3.76）, used in semi tractors, dump trucks, and short cargo models, and the long 162英寸（4.11）, used in tankers, long cargo models, and the U9 chassis cab (measurements are from the centerline of the front axle to the centerline of rear bogie). All models had 7.50-20” tires and dual rear tires. 6x4 models, intended for on road use only, were rated at 5 tons (4536 kg), twice the 6x6’s off-road rating.[3] [12]

Cab

The US6 carried the design of Studebaker’s civilian truck cab, although it was modified for military use. Studebaker trucks were different from other 2 ¹⁄₂ 6x6 trucks built for the war effort of the USA because vent windows were included in each door. These vent windows were separate from the main window that rolled down into the door-frame and could be swung out to help with the truck cab's ventilation.

Studebaker also designed the open-type military truck cab which was featured on the GMC CCKW (later models), but their major customer, the USSR, preferred the closed cab for their generally harsh (cold-weather) climate. While Studebaker's open-type truck cab became the American standard, production of the US6 with the closed-type truck cab was restarted after only 10,000 units of the former.[3]