Service Manual

7-4
WPM Drive Systems Manual
WHEELPINIONCLUTCH
QuickTest
If you are unsure that the keys are disengaging properly,
stop the mower, shut the engine off and push the mower
forward a few inches. If the keys disengage the system
is working correctly. Start the engine and engage the
drive, if both engage they are OK. If one or the other
do not engage or disengage properly try greasing the
pivot arm. Use #2 lithium grease and only one or two
pumps from a hand grease gun. If grease does not help
disassembly is necessary.
RearHeight-of-CutandWheelPinionClutch
-Disassembly
The rear height-of-cut system and the wheel pinion
clutch can be serviced with the transmission in or out of
the unit. For information on removing the transmission
from the unit, see Transmission – Removal, page 3-3,
5-5 or 5-6 depending on mower type.
1. Remove the shoulder bolt securing the wheel and
tire assembly to the pivot arm and remove the wheel
and tire assembly complete with shoulder bolt,
spacers, wheel cover, and nylon locknut.
2. Remove the special retaining clip at the end of the
output shaft and pull off the following six wheel
pinion clutch components:
• Spring
• Internally tabbed thrust washer
• Wheel pinion
• Wheel pinion key
• Clutch washer
• Friction ring
3. Remove the inner special retaining clip from the
output shaft and remove the following components:
• Internally tabbed thrust washer
• Externally tabbed thrust washer
• Pivot arm and spring arm assembly
• End cap (if desired)
TestforFunction
Function
The rocking keys provide a differential action by
engaging and disengaging each drive wheel individually.
When the drive is engaged and the axle begins to turn,
friction between the friction ring and clutch washer cause
them to rotate the tail on the key. This results in the main
part of the key engaging the teeth on the inside of the
pinion gear.
Should one or both wheels turn faster than the axle,
the pinion rotates and pushes the key back down into
the groove. The pinion can now roll freely over the key.
When turning the inside wheel will drive the mower. The
outside wheel must turn faster and overrides the key.
When the mower is straightened out the pinion is no
longer turning faster than the axle so the key re-engages
the pinion.
To operate this system, practice the following. Walk
along at a normal pace. When you stop walking, keep
your elbows at your sides. The mower will continue
forward for a few inches due to its momentum. As
the mower rolls away, the drive will disengage as
the Personal Pace/ Easy Stride handle extends and
disengages the transmission. From the point where the
transmission is no longer turning the axle, the mower
must roll about 1-1/2” forward. This causes the pinions to
rock the drive keys to the disengage position. At this time
the mower can be pulled backward with minimal effort.
When the drive is engaged and the axle begins to turn
the keys should re-engage.