Pick a quiet road with a smooth surface so that noises well be herd without difficulty. Use a road with hills where the clutch must work especially hard, if possible. Drive the vehicle long enough to warm up the clutch to operating temperature. Stop the vehicle frequently and drive again, shifting through each of the gears. If possible use the clutch on a hill. During the test rive look for these conditions: whirring nose, gear clash, knocks, squeaks, grinding nose, pedal pulsation, vibration, chatter, slippage.
If whirring, light grinding, heavy grinding, and snapping conditions exist when the clutch pedal is depressed the problem is almost surely with the release bearing. In this case the release bering may have failed internally, or it may be turning one the hub. Be sure to inspect the hub and the pressure plate levers or fingers. In either case, the transmission will have to be removed to replace the bearing and /or the hub.
When noise similar to the above occurs, but with the transmission in gear and the clutch disengaged, the trouble can be the pilot bearing in the flywheel. In this case, the transmission input shaft has stopped, but the flywheel is turning, thus making the pilot bearing work.
Another noise in this class may be from the transmission gears. The noise should stop when the clutch is disengaged. The clutch may not disengage if the facing is warped or torn, if the linkage or pressure plate adjustment is worn, or if the clutch disc is sticking to the flywheel or pressure plate.
Still another possibility is the sound of the clutch disc rivets or steel portion of the clutch disc rubbing against the flywheel or pressure plate.
Gear clash clash is sometimes the result of not disengaging clutch. To check this, start the engine and very carefully push the shift lever toward low (first gear until the gears just begin to touch each other, hold at this position and slowly push the clutch pedal. When the clutch pedal is approximately 25 mm from the floor, the gears should stop ribbing and a quiet shift should be possible. Noise from rubbing gears when the vehicle is moving is usually due to transmission problems.
Knocks are caused by large pieces of metal contacting one another rapidly. This means that some parts are not secure, are worn, or are loose. A mall knock is normal due to driveline clearances. If the knock is a single one when engaging or disengaging the clutch, it may be the linkage passing a high resistance point or an obstruction, or it may be interference with an adjacent component. A worn crankshaft thrust Bering will knock when the clutch is rapidly disengaged. One or two out of adjustment release levers (fingers) will cause a knocking noise when the release bearing first contacts them. Steady knocking in the clutch area can be a loose flywheel or pressure plate, bad engine or transmission bearing, a broken transmission bearing, a broken transmission gear, or loose parts bouncing around in the clutch housing.
