These vehicles are equipped with an Allison HT 740 automatic transmission, incorporating four speeds forward
and one reverse. The transmission features:
Torque Converter. A simple, 3-element torque converter transmits power from the engine to the transmission
gearing. The torque converter serves as both a fluid coupling and a torque multiplier.
Lockup Clutch. This clutch automatically locks the turbine element of the torque converter to the flywheel. When
the turbine approaches the speed of the pump, hydraulic pressure automatically applies the lockup clutch. With the
lockup clutch applied, engine output is directed to the transmission gearing at a 1: 1 speed ratio. A decrease in speed
automatically releases the lockup clutch.
Planetary Gearing, Clutches. Three planetary gear sets establish the four forward speeds and one reverse in the
HT 740 transmission. The planetaries are controlled by five hydraulic-applied clutches. All gearing is in constant mesh.
Control Valve Body Assembly. The control valve body assembly is the brain of the transmission. It is
hydraulically operated. Oil passages, valves, and springs are designed to allow the flow of hydraulic fluid to pre-
designated areas. Through variations of pressure and spring tension, the components in the valve body are hydraulically
moved at the precise time, redirecting fluid to pre-selected locations.