Service Manual

General Information
Four-Matic
TM
4WD Over-Running Clutch Operation
Th ere are two hydraulic drive motors on the
Groundsmaster 455-D, 4WD; one for the front axle and
one for the rear axle. The drive for the rear axle incor-
porates an OVER-RUNNING (ROLLER) CLUTCH THAT
TRANSMITS POWER ONLY IN THE FORWARD DIRECTION
(Fig. 3).
Front and rear axle gear ratios and tire sizes were
c
arefully selected so that during normal operation, the
REAR AXLE SHAFT TURNS SLIGHTLY FASTER THAN THE
REAR AXLE MOTOR
.
Any time the front wheels begin to slip (such as when
c
limbing a steep hill), the forward movement of the
49 RPM
50 RPM
49 RPM
49 RPM
Rear
Axle
Unlocked
Locked
Motor
Shaft
Rear
Shaft
traction unit slows. This causes the rear axle shaft
speed to slow down. As soon as the rear axle shaft is
turning the same speed as the rear motor, the roller
clutch will engage and power will be transmitted from
the rear motor to the rear wheels – four wheel drive
(Fig. 3).
When the traction unit is turning, the rear wheels swing
out
in a larger arc and must travel faster than the front
wheels. In this condition, the rear wheels and axle shaft
are turning faster than the rear motor and the roller
clutch is disengaged (Fig. 4).
NOTE: The Four-Matic four wheel drive system may not
oper
ate properly if the tires are replaced by different size
tires, or if proper tire pressure is not maintained.
Figure 3
Figure 4
Axles and Brakes
Groundsmaster
®
455-D Page 6 - 3 General Information