Service manual

1-2 WPM Drive Systems Manual

WORM DRIVE TRANSMISSION

GENERAL

There are two versions of the worm drive transmission.

The ﬁ rst is a clutch type and is used on 21” front wheel

drive mowers. The second version is constant mesh and

is used on International 48cm rear wheel drive mowers.

This is a worm and helical gear transmission. The worm

shaft (input shaft) is driven by a belt from the engine

crankshaft. A spring which hooks into the tab on the

front of the transmission (where the roll pin is) and to

Fig 001 ﬁ g 1

INTERNALLY CLUTCHED

Description

the mower housing, pivots the transmission forward to

maintain tension on the belt.

The worm is in constant mesh with the helical gear. The

clutching action is provided by a sliding clutch jaw. A shift

fork moves the clutch jaw to engage and disengage the

transmission. When the clutch jaw engages the helical

gear, power is transferred from the clutch jaw to the

sleeve inside the clutch jaw. The sleeve is pinned to the

axle. The axle then begins to rotate (Fig. 001).

A. Belt E. Shift Fork

B. Spring F. Sleeve

C. Helical Gear G. Input Shaft

D. Clutch Jaw (worm shaft)