Most common clutch troubles are incomplete engagement and incomplete disengagement.
Incomplete engagement (the clutch slips while engaged) could be caused by an incorrect linkage adjustment (no clearance between the release bearing and release levers), oil on the linings of the friction disc, worn friction disc linings, or weakening of the pressure springs. In this case, the tractor or automobile "pulls" poorly, and burnt friction linings can be smelled in the driver's cab.
Incomplete disengagement (the clutch spins or drags when disengaged) may result from an incorrect linkage adjustment (excessive clearance between the release bearing and release levers). Or, this could be due to internal clutch troubles, such as linings torn or loose from the friction disc, a warped friction disc or pressure plate, improper clutch adjustment (nonuniform clearance between the release bearing and release levers), or binding of the friction disc hub on the transmission input shaft. In this case, the transmission gears will be difficult to shift and will clash and grind when shifting.
Internal clutch troubles call for overhauling the clutch mechanism. However, if the trouble is in the linkage-if it is binding or out of adjustment-the linkage can be lubricated and readjusted.
CLUTCH MECHANISM AND LINKAGE ADJUSTMENT. During operation, the friction linings of the driven disc, or discs, and the friction surfaces of the flywheel and pressure plate suffer wear. As a result, the initial setting of the clutch mechanism and linkage is gradually disturbed, with the clutch pedal free play diminishing progressively. The free play is the amount of clutch pedal free travel before the clutch begins to disengage, and it must be sufficient for the release bearing to stay clear of the release levers when the clutch is engaged. Unequal clearances between the individual release levers and the release bearing may cause the pressure plate to skew, disturbing normal clutch operation (the clutch may drag when disengaged or chatter while engaging).
The free play of the clutch pedal is adjusted by varying the length of operating rod. If the clutch is equipped with a brake, brake operating rod should be removed before making the adjustment. Also, the clutch pedal should be relieved of the booster spring pressure, if a booster is used, by screwing in fulcrum pin as far as it will go.
The clutch brake, if one is used, is adjusted after the clutch pedal free play is adjusted properly. This is done by varying the length of brake operating rod or by changing the position of the brake shoe with the aid of adjusting nut. The brake should be adjusted so as to ensure that it is applied only after the clutch is completely disengaged.
The release levers are adjusted by means of adjusting screws, their lock nuts being loosened beforehand. This adjustment is usually made when overhauling the clutch mechanism.
When operating the tractor or automobile, keep in mind that the clutch should be disengaged quickly and engaged only gradually. A sudden clutch engagement may cause damage to transmission components. Never "ride" the clutch pedal, by resting a foot on the pedal, for this partly releases the clutch, causing clutch slippage and rapid wear of the clutch disc friction surfaces.