Manual transmission cars and trucks all have a clutch that needs periodic adjustment and repair or replacement. The clutch system consists of the following components:
CLUTCH DISK (or DISC):
The clutch disk is covered with a special lining (used to be asbestos: now it's a fiberglass composite). The lining material is similar to the material used on your brake pads. When you release the clutch and let it "slip", you are wearing the clutch lining material. When the lining material is all worn away, you need a clutch job, just like you need a brake job when your brake pads wear out. The Clutch disc is sandwiched between the pressure plate and the flywheel.
Click here for Pictures and Diagrams of Clutch Plates
The pressure plate is is a spring loaded device which presses the clutch disk against the flywheel. It should be replaced with each clutch job because its springs can weaken and its surface can warp or become unevenly worn, causing slipping, chattering, or locking up of the clutch. Reusing the same pressure plate can make a clutch job fail before its time.
Click here for Pressure Plate Images
THROWOUT BEARING (OR RELEASE BEARING): The throwout or release bearing presses on pressure plate to release clutch. It should also be replaced with each clutch job.
Click here for Pictures of throwout or release bearings
PILOT SHAFT BEARING OR BUSHING:
(Some Cars) The pilot bearing or bushing supports the outer end of the transmission input shaft. It is located in the center of the flywheel or end of crankshaft.
Click here for Pictures of pilot bearings
The flywheel is the other surface the clutch disc rubs on. It often must be resurfaced (turned) when the clutch is replaced.
Click here for Pictures of Flywheels
Several types of linkage are used to connect the clutch pedal to the throwout bearing and pressure plate. These include:
Many cars have a clutch cable linkage. A cable can be run around corners and allow flexibility of car design. A clutch cable can wear out, bind and get stiff, or break.
A hydraulic clutch linkage is even more flexible than a cable. A hydraulic clutch has a clutch master cylinder behind the clutch pedal and a clutch slave cylinder at the transmission. Both cylinders, master and slave, can fail and cause a clutch pedal that won't release the clutch. (low pedal, grinds going into gear)
Rod and bellcrank linkage
The rod and bellcrank linkage has a series of rods and pivots that connect directly to the clutch. This is probably the most reliable linkage, usually outlasting the car. Unfortunately it's also the least flexible and isn't found on many cars because of that. Mostly found on trucks, vans, and older vehicles.
Symptoms of a misadjusted or malfunctioning Clutch Linkage
A clutch linkage adjusted too tight can cause slipping and wear out the clutch prematurely.
A clutch linkage which is too loose or fails can make the clutch not release and make it impossible to get into gear. On some vehicles a chattering clutch on release can be caused by a bad clutch linkage.
Air Cooled VW Beetle clutch linkage problems
The air cooled rear engined VW Beetle had a cable operated clutch. This cable ran through a tube which was mounted in 3 places inside the car body. When a weld on one of those tube braces breaks, the clutch will chatter and jerk on release, as well as giving adjustment problems. You have to know where to cut on the body, then cut a hole in the "tunnel" in the middle of the car and re-weld the brace.
(Engine rev's up but car speed does not increase, or rpm's start going up as you go up a hill) Slipping is either a bad clutch disk or misadjustment of the clutch.
Won't go into gear or hard to shift or low pedal
If your car or truck won't go into gear, grinds when you shift into reverse, or is hard to shift or has a low pedal, either a bad linkage (cable or hydaulic failures are common) or bad pressure plate is probably the problem.
Clutch makes noise
A whirring noise which changes as you press and release the clutch pedal can be a throwout or pilot bearing.
NOTE: I have a recording of a bad throwout bearing in my NOISE LIBRARY
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Gainesville has been my home since 1974, and I've loved Gvl and the Gators since I came here in the fall of 1974 to attend the University of Florida. I loved it so much I stayed and opened my car repair business. Originally it was out of the back of a 1963 Chevrolet wagon, but in 1977 a fellow mechanic and I opened an auto repair shop with actual walls, etc. I stayed in the same location for 26 years, and recently moved my operation to property I bought 15 miles east of Gainesville. I am doing most all the repairs myself now, having reduced my overhead from $1500 per month to practically nothing. I do work by appointment only. I mostly work only on my established customers cars, but I will occasionally take on new clients. E-mail me and I will either make arrangements to look at your car, or I will recommend you to someone who will.
George G. Scott, Jr.