TROUBLESHOOTING THE HMMWV - OD1616 - LESSON 1/TASK 1
multiple disc clutches, one sprag and one roller, and two friction
The torque convertor smoothly couples the engine to the
planetary gear through oil, and hydraulically provides additional
torque multiplication when required. The compound planetary gear set
gives three forward ratios and one reverse. The changing of the gear
ratios is fully automatic in relation to vehicle speed and engine
The torque from the engine is transmitted to the
transmission through the flex plate. Vehicle speed and engine torque
signals are constantly fed to the transmission to provide the proper
gear ratio for maximum efficiency and performance at all throttle
(3) Transfer Case.
The transfer case
simultaneously. This condition means the vehicle is always in four-
wheel drive. The transfer case allows for selection of three driving
ranges and a neutral position.
The transfer case used on the HMMWV
is a New Process 218 (MOD), two-speed, locking, chain-driven
The transfer case holds 3.5 quarts of Dexron II
There are four shift lever positions for transfer
case drive ranges. The first is "L" which represents low lock. This
position is used only when the vehicle is climbing or descending
steep hills, or operating in deep mud, sand, and snow.
position is the "N" or neutral position. This position is used when
the vehicle is disabled and must be towed. The next position is "H"
This is used when operating the vehicle under normal
driving conditions and when fording. The last position is the "H/L"
or high lock position which is used when driving through mud, sand,
snow, off road, or any other slippery road conditions.
(4) Propeller Shafts.
transfer case to the differentials.
Universal joints, located at
both ends of the front and rear propeller shafts, permit inline
driving power between the transfer case and the differentials even
though they are mounted at different angles.
(5) Differentials. The differential is a gear system that divides
torque between the axle shafts