Hints for the Motorist

Bay of Plenty Times, Volume LXXVII, Issue 14928, 16 March 1949, Page 4

Hints for the Motorist

Y albert l.clough —-^^ sa

Many Faults Must Be Remedied To Keep Clutches Clutching

"RIDING" OR SLIPPING COMMON CAUSE OF TROUBLE * More Clutch Troubles probably are caused by poor driving than by any normal wear and tear. "Normal" excludes such thing's as taxicab work in city traffic where stop and start is the the rule, or trucks on construction jobs where there is necessarily slippage and heat in starting heavy loads. Worst thing that can happen to a car or truck clutch, other than the above special conditions, is to be operated by a driver who, rides with his foot ,on the pedal, holding it partly depressed. The driver who holds his automobile on a slight upgrade by slipping the clutch does equally great damage, and only the fact that his crime is less frequent keeps him from being in the repair shop all the time.

No clutch repair will stand "riding" or slipping, and no mechanic should let a customer leave the shop without warning. By driving with the pedal slightly depressed, the clutch throwout bearing is constantly pushing against the pressure plate release mechanism. This in turn will affect the amount of slippage betwen the clutch plate and the flywheel. Automobile clutches are not intended to slip constantly. The material on the clutch plate is .similar to brake lining and by friction, locks the engine to the transmission. If the driver were to go down the road with his foot on the brake pedal, the brakes would soon overheat and burn up, and if the clutch facing slips or rubs steadily, the lining will soon be rubbed off and the entire clutch mechanism become overheated.

j brake lining replaced before the rivets protrude will save scoring of the brake drum. If the clutch lining is worn down too far it will pull away from the clutch plate and cause scoring or grooving of the pressure plate. There is no way to tell from outside when the lining is worn down to the rivet's but as a general rule, when you are near the end of the linkage adjustment you are quite sure to be reaching the rivets. It is for this reason that no attempt should ever be made to "trick-up" a final clutch adjustment. Rather, remove the clutch and fix it right. Grabbing clutch its caused by: a. Oil or grease on facings (this may also cause slipping clutch). b. Several weak springs in pressure plate. c. Loose facings. d. Broken springs in pressure plate. e. Loose pressure plate hub. f. Improperly adjusted release fingers in pressure plate. Dragging or poor Releasing Clutch caused by: a. Improperly adjusted pedal. b. Pilot bearing in flywheel badly worn or seized to mainshaft. c. Improperly adjusted pressure plate. d. Foreign material or grease on facings. o. Engine idling too fast. f. In the case of Chevrolets, the threaded clutch yoke pivot having loosened up in bell housing. Clutch Chatter is caused by: a. Loose or oil rotted motor supports.

Adjustment of the clutch externally is also important; all cars and trucks have a point in the pedal linkage mechanism whereby pedal travel before disengagement can be controlled. On some cars, the adjustment can be made from under the hoed and on others is made from under the car.

When the driver has been "riding" the clutch or there has been a lack of free play in the pedal, pressure plate fingers which rub against the throw-out bearing may become badly worn.

When rebuilding a clutch assembly, the pilot bearing in the centre of' the flywheel should not be overlooked. This bearing cannot be lubricated without disassembling the clutch. Remove it (most cars use a small ball bearing), wash with kerosene, inspect and repack with fibre grease. A dry or worn pilot bearing can cause a high pitched noise or worse "still, can allow the main shaft of the transmission which it supports, to run off true, causing poor clutch operation and perhaps eventual shaft failure.

b. Oil soaked (from rear main bearing or excessive throwout bearing lubri'cation) clutch facings.

c. Looseness in transmission, rear axle or universal joints. d. Loose or improperly adjusted oressure plate. e. Bad'y worn pilot bearing in flywheel allowing the transmission mainshaft to run out of centre.

Present day cars are equipped with factory pre-lubricated throwout bearings which, for the normal life of the bearing, require no attention. There are, however, many older cars on the road having oii cups, grease cups of lubrication lines to the throwout bearings. Care must be exercised that too much lubricant is not used or it will work its way forward and soon have the clutch plate ruined. Again comparing car brakes with clutches, over lubrication of rear wheel bearings wi'll get grease or oil on the brake lining; over lubrication of throwout bearings will get grease or oil on the clutch lining. Various clutch complaints and their causes can be listed as follows: a. Badly worn facing. b. Driver "riding clutch." c. Oil or grease on facings (this can also cause grabbing). d. Improperly adjusted pedal. e. Weak pressure plate springs. f. Pressure plate finders improperly adjusted.

Clutch Noise is caused by: a. Dry of worn pilot bearing in flywheel. b. Broken springs in pressure nlate or clutch plate hub. c. Dry or worn throwout bearing, cl. Throwout bearing riding too tightly against the release fingers.

c. Dry or rusty splines on clutch plate and transmission main shaft.

f. Worn front beari'ng in transmission (this can sound as if it is coming from the clutch). g. Loose hub in clutch. h. Badly worn or loose clutch yoke allowing the throwout bearing to touch the transmission main shaft.

i. Misalignment between the transmission, clutch assembly and engine.

Clutch pedal free travel (the distance the pedal moves before disengagement begins) will vary from three quarters of an inch to about two inches depending on the individual car manufacturer's requirements. If the pedal travel before disengagement of the clutch becomes too great, the clutch plate releases too slowly or not at all, making it difficult to shift gears. General indication of this condition is the clashing of the gears when the shift lever is moved from neutral into low or second. Lack of pedal travel has the same result as "riding" the clutch pedal with the foot. The spring and linkage mechanism will constantly press against the throwout bearing causing partial release and slip. When slippage occurs, the pressure plate is likely to become overheated.

After a number of adjustments it will be found that the clutch linkage will be unable to compensate for further wear. Then the clutch assembly will have to be removed and rebuilt.

Engine rubber supports which have become soggy from oil rot are likely to cause clutch chatter. At. time of clutch overhaul, check the supports for lack of resiliency and replace them if need be.

Internally, clutch plate and pressure plate wear are the most frequently found troubles. If the clutch plate is replaced before the lining is worn below the rivet , heads, the pressure plate and flywheel will not be grooved by the rivets; similarly