Series Land Rover clutch system operation.
The clutch is basically a vertically arranged sandwich with a thin clutch driven plate('clutch disc'), having high friction linings, as the filling. The engine-side 'slice' is the flywheel and the gearbox-side 'slice' is the clutch pressure plate. Springs press the pressure plate towards the flywheel, squashing the filling. It is the job of the clutch actuating mechanism to relief this pressure and thus allow the 'slices' to rotate relative to each other i.e. to disconnect the Land Rover's engine from the gearbox.
When the clutch pedal of a series Land Rover is depressed, fluid from the clutch master cylinder is pushed under pressure to the clutch slave cylinder. The push rod from the slave cylinder then causes the clutch release shaft to rotate a little. This has the effect of pushing the release bearing and sleeve forwards and allowing the pressure plate (gearbox-side 'slice') to move towards the rear. Pressure is now taken off the clutch disc and it can spin freely in relation to the flywheel.
This 'squeal' or low note rubbing sound is usually heard when the clutch pedal of your series Land Rover is depressed prior to selecting gear. The sound disappears once the gear is selected . It is caused by wear in the Land Rover's clutch release bearing and this item then needs to be replaced. It is a simple procedure but either the gearbox or the engine has to be removed from any Series Land Rover to accomplish it. Not 'riding' the clutch at traffic lights etc will prolong the life of this bearing.
This is caused by lack of friction between one or both surfaces of the clutch disc. With any Series Land Rover, it is most often the result of oil leaking onto the clutch disc through overfilling the engine with oil or a damaged oil seal in the flywheel housing or gearbox. It can also be caused by a faulty pressure plate, wrongly adjusted slave cylinder push rod or a distorted clutch disc caused by fitting it wrongly. Lack of sufficient pedal movement can also cause it.
Clutch slip is most easily diagnosed by suddenly depressing the accelerator when the vehicle is moving. A noticeable increase in engine speed without the corresponding increase in vehicle speed indicates that the Land Rover's clutch is slipping.
This occurs when the pressure plate does not completely free itself from the clutch disc. In a Series Land Rover, it can be caused by air in the fluid or a leak in the fluid from the master cylinder, slave cylinder or pipes; the movement of the slave cylinder push rod is excessive; the clutch disc is sticking on the gearbox shaft splines or carbon deposits (from burning oil) on the clutch disc are causing it to stick to the pressure plate.
Clutch spin most often causes difficulty in selecting first gear from rest, difficulty in changing gear or sudden take-up of drive when the clutch pedal is released at the extreme end of its travel. If allowing a short pause between pressing the clutch pedal and selecting gear reduces the problem then this indicates clutch slip as the cause.
This would most frequently occur if the clutch is suddenly released with the Land Rover in first or reverse gear. It is usually the result of the clutch disc not becoming completely free from the pressure plate when it should. The whole Land Rover judders. Common causes are loose or very flexible engine and/or gearbox mountings; oil on the clutch disc or a poorly fitted clutch. The clutch pedal may be sticking, the flywheel may have excessive runout (i.e. bent slightly or not fitted correctly). Broken or weak pressure springs or diaphragm. Alternatively, in a Series Land Rover, worn propshaft joints or bent primary pinion shaft could produce an effect similar to clutch judder.
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