Troubleshooting Clutch Issues

Premium Member

Here are some quick and easy troubleshooting tips for common complaints about performance clutches we have seen over the years.

Clutch Slips
It’s probably wearing out. Sometimes this can be caused by cable adjustment on cars so equipped. Go to the arm where the clutch cable connects to the throwout fork of the transmission. Wiggle the cable, it should feel slightly loose. If it is drum tight, loosen the adjuster as per the service manual for your car and put a little play in it. On hydraulic clutches, check the adjustment of the rod from the clutch pedal to the clutch master cylinder, this might be adjusted or staged too far out. On some cars the rod between the throwout arm and the slave cylinder is adjustable. If the clutch stops slipping you are most likely ok for a while. Otherwise you need a new clutch. If you just added a lot of power to your motor with nitrous or forced induction, it probably needs a HD clutch!

Clutch Pedal is suddenly real stiff
The clutch cable is wearing out and is about to break or needs lubrication. The fraying broken ends of the cable are jamming into the housing and gumming things up. You need a new cable. On both cable operated and hydraulic clutches the throwout fork pivot may be seizing up or about to break, inspect lubricate or replace this part.

My clutch pedal sticks to the floor when I speed shift
Your clutch is overcentering. You need to reduce the cable pull so the clutch pedal will only pull enough cable to just disengage the clutch. Likewise on hydraulic clutches, you may have to adjust the clutch cylinder staging at the pedal to limit its engagement.

Clutch pedal engagement height starts to change all of a sudden
The throwout bearing fork is bending or starting to break. This can happen if you have a heavy duty clutch with a really heavy diaphragm spring.

Engine starts to make a deep knocking noise which changes when you push the clutch pedal in.
You poor bastard. The crank thrust bearings are starting to fail. This can happen if you have a clutch with a heavy diaphragm spring and is a good case for using a twin disc clutch rather than a really heavy diaphragm spring single disc. Second generation DSM’s are prone to this.

My transmission grinds when I shift
Several things can cause this. If it grinds or shifts real stiffly in every gear, I would investigate to see if the clutch adjustment is allowing full disengagement of the clutch. If that is ok, the pilot bushing in the crank may be wearing out. If it grinds when only going into one or two particular gears which can be prevented by double-clutching, the syncros may need to be replaced. Sometimes marginal syncros can be stretched a while by going to a different brand of high quality gear oil. A sometimes occurrence is that your throwout fork or pivot has bent, check it. With a hydraulic clutch, look for fluid leaks at the slave cylinder and clutch cylinder then bleed the system. Some hydraulic clutches have built in accumulators in the systems that are meant to smooth shifts. When they start to fail, they can delay the transfer of motion from your foot to the slave cylinder. Some people remove these to help speed shifting.

My clutch won’t disengage even when I push the clutch pedal in
If the pedal feels slightly stiff but otherwise normal, a disc hub spring has probably broken out and is wedged in the pressure plate. In extreme cases the pressure plate diaphragm spring has broken or the diaphragm spring fulcrum has failed. If this is the case the pedal gets real soft. This failure is not very common. Sometimes the throwout bearing arm or pivot bends or breaks.

The clutch pedal offer resistance to pushing but the car won’t move, like it’s in neutral
Bad news, your clutch disc has probably burst. Replace disc and any other damaged parts.

My transmission makes a whirring or rough rumbling noise that goes away or changes when I push in the clutch pedal
This doesn’t have anything to do with the clutch. The transmission input shaft bearing is beginning to wear out. The transmission is in need of a rebuild.

My car shifts stiffly, especially in cold weather
This doesn’t have anything to do with the clutch. The trans fluid is getting thick and gummy in the cold, try a high quality synthetic gear oil.

My brand new kevlar clutch disc judders
You either did not resurface the flywheel correctly or contaminated the disk with fingerprints, oil or grease causing the disc to glaze. Remember flywheels used with kevlar discs must be carefully resurfaced and the clutch must be broken in with easy driving for 500 miles. Any fingerprints or oil must be carefully cleaned off with contact cleaner or brake cleaner before installation. A lightly glazed Kevlar disc can sometimes be restored with light blasting with glass beads.

My metal disc judders
This is normal, metal discs usually have no marcel spring and no hub springs. Live with it or make less power and put in a sprung hub, marcel equipped clutch disc.

My solid hub, all metal, three puck disc clutch judders and jerks real bad
This is normal. A race disc in not streetable. Don’t be a sissy.

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