INTRODUCTION TO THE HMMWV - OD1615 - LESSON 2/TASK 1
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. The second 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" or high. This is used when operating the vehicle in 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 slippery road conditions.
e. Propeller Shafts.
case to the differentials.
Universal joints, located at both ends of the
transfer case and the differentials even though they are mounted at
The differential is a gear system that divides
torque between the axle shafts allowing them to rotate at different speeds
The dual drive differential is a limited slip (torque
It resists spinout by transferring more torque to
the drive wheel that has the most resistance to spinout.
differential has no such provision.
The differentials are mounted up
between the frame rails to minimize drive line vibration, external damage,
and to increase ground clearance.
The front and rear differentials are
identical and are interchangeable, providing that the yoke is changed. The
differential uses gear oil (GO) 80/90.
g. Axle Half Shafts.
The HMMWV utilizes axle drive shafts (half
shafts) to accommodate the independent suspension system.
The purpose of
the half shafts is to transfer torque to the wheels from the differential
through the geared hub.
The unit is basically a one-piece assembly with
boots on both the inboard (differential) and outboard (geared hub) ends.
The inboard end is bolted to the differential side flange and the outboard
end is splined to the drive gear of the geared hub.
The inboard boot
encloses a constant velocity joint which accommodates the in-and-out and
angular motion of the axle drive shaft with no change to either system.