Troubleshooting Clutch Issues
Jump to your problem:
What is it?
This is one of those clutch problems where you don’t have it at all, or you have some degree of it. At one end of the spectrum, the transmission grinds or clashes going in to gear or it’s hard to get into gear. With the clutch pedal pressed in and the car in gear on a flat surface, the car may creep forward. On the other end of the spectrum, the car won’t go into gear at all. With the transmission in gear and the clutch pedal depressed, the engine will stall.
First make sure the car isn’t creeping because of spindown which is totally normal. Spindown simply means that the clutch disc continues to spin for several seconds after being disengaged. This test will only work on an unsynchronized gear, like the TKO 5-Speed’s reverse gear. On a flat surface, depress the clutch pedal, shift into neutral and wait 30 seconds. Shift into reverse. It should go in smoothly and if it does, the creeping was caused by spin down and you have nothing to worry about. If it clashes, you have a clutch drag problem.
What causes it and how can you fix it?1) Mechanical clutch linkage can prevent the clutch from fully disengaging. Disconnected or loose linkage or a dry hydraulic system will usually be indicated by a pedal that requires little to no effort to depress. A hydraulic release system could be low on fluid from a leak, have air in the system, or have pedal linkage alignment or installation problems.
First check all moving parts and connections, they may have come apart, been assembled incorrectly, or become damaged. Check the clutch fork and make sure it’s properly connected to the throw out bearing. Improper assembly is a common issue customers have with GM clutch forks. See our tech article on installing mechanical or hydraulic linkage.
For hydraulic systems, check the reservoir for fluid; there could be a leak in the system. If the pedal feels spongy, there’s air in the system. Repeat the bleed process. Also, check the pedal linkage is properly installed to assure the hydraulic master cylinder has full travel to completely disengage the clutch.
2) Too much free pedal travel can cause the pressure plate to back off, but not completely, keeping in contact with the clutch disk even with the pedal pushed to the floor. This is the most common cause of clutch drag and the solution is to adjust the clutch to eliminate the free travel, trimming the bumper stop if necessary.
3) Another possible cause is misalignment of bellhousing to engine block. We have a great video on how to check the alignment here.
4) The least likely and final cause could be a worn or frozen pilot bearing, a sticking or warped disc, or a warped pressure plate or flywheel. A worn disc could become overheated and weld itself to the pressure plate. In this case, your clutch linkage would work as it should, but the engine and transmission are always mechanically connected, causing the clutch drag. You’ll have to replace the damaged parts.
What is it?
If you step on the gas and the engine responds by increasing the RPM, but your car maintains the same speed or barely speeds up, the clutch disc is slipping between the flywheel and pressure plate. This problem needs to be solved early at the first sign of trouble, the longer you drive with it the more damage you’ll do.
At first, you’ll only notice it only on initial and hard accelerations, but later it’ll happen when you shift up or down and on any kind of acceleration. Eventually, the clutch disc will no longer have enough grip to move the vehicle. The worst part is not only have you exhausted the life of the clutch disc, the excessive heat from the disc will damage both the flywheel and pressure plate.
What causes it and how can you fix it?
1) Improperly adjusted clutch linkage can cause a clutch to slip, but if the clutch is slipping badly, the clutch disc is usually glazed and too badly worn to be fixed by adjustment and will need to be replaced. A glazed clutch disc will have no grip and if the clutch disc is completely worn down, the apply springs will not put enough pressure on the pressure plate to hold it tight against the flywheel.
However, if you catch the slipping early, the first thing you should do is check the clutch linkage adjustment. If the linkage is adjusted to have no free play and the throwout bearing is applying constant pressure, the clutch is not fully applied and it will slip.If the clutch fork return spring is not connected, the pedal will have no free play, but the clutch will not slip in this case. The clutch will fully engage and the throwout bearing will ride the release levers or fingers, but will not apply pressure. So do not mistake this lack of free play as a sign of misadjustment.
2) If the engine’s rear seal is leaking, the clutch disc can become soaked with oil and will need to be replaced even if it is not worn down. Fix the leak, or this problem will reoccur.
3) If you drive through deep water, the clutch disc can get wet and slip. Performance will usually return to normal once the clutch disc dries.
4) If the flywheel, clutch disc or pressure plate is warped, the pressure plate will not make good contact with the disc which can cause the disc to slip or chatter. Replaced the warped part(s).
5) If the clutch pedal is pressed with little or no effort, it may be a sign of weak clutch apply springs. Weak springs could be from the manufacturer, the clutch could be intended for a smaller engine or lighter car, they can become weak from overheating, or just from old age. Replace the pressure plate.
Dumping or popping the clutch by increasing the engine speed and suddenly releasing the clutch pedal will engage the clutch almost instantly building up heat immediately and putting tremendous stress on the clutch and the entire drivetrain. This abusive driving can glaze a disc within seconds, causing slippage. It could also cause even more severe and costly damage by sheering the bolts off the flywheel, clutch cover, or bellhousing and can strip the clutch disc splines and break the input shaft on your transmission.
7) If the clutch disc isn’t seated in, it’ll slip. Without overheating the clutch, make 30-40 normal starts.
What is it?
If the clutch engages with a jerk or shudder no matter how slowly and carefully it is applied, it’s grabbing. It may also be a series of grabs that feel like bucking. If severe enough, it could cause damage to the universal joints or other parts of the drivetrain.
What causes it and how can you fix it?1) This time, the first thing to check isn’t the clutch. Loose engine, transmission and transaxle mounts can create the same sensation. Also check all bellhousing and transmission bolts for tightness. Cheap and easy fix!
3) Rarely, worn splines on the clutch disc hub flange or transmission input shaft, or a warped clutch disc, warped pressure plate, or flywheel can cause grabbing as can a worn or misaligned clutch fork making the throwout bearing apply uneven pressure. Replace or adjust parts. To prevent warping your pressure plate or flywheel during installation, the clutch pressure plate bolts must be installed and torqued to spec using a star pattern. Flywheel bolts must also be torqued to spec using a star pattern.
What is it?
You’ll hear a rapid clunking or rattling noise and may feel a small vibration. Rather than occurring when the clutch is fully engaged, it occurs during engagement, as you move the pedal. Closely related to grabbing, but still different, clutch chatter is heard more than felt. What you hear isn’t actually the clutch, but the vibration of the linkage and drivetrain.
What causes it and how can you fix it?1) Did you check the runout on your bellhousing? This isn’t the only problem misaligned driveline components can cause. Plus, not doing it will void the warranty on your transmission. Do it! We have a video you can follow along with while you do yours or call us, we’re always ready to help.
What is it?
Unlike clutch chatter which occurs as the pedal is pressed, clutch vibration occurs while the clutch is fully engaged and will vary with engine speed. There will often be noise and vibration, but sometimes noise is a secondary symptom.
What causes it and how can you fix it?
Of course, a vibration can come from a variety of sources, so you’ll want to rule out other possibilities.
If the vibration occurs only when the vehicle is moving, it’s probably not the clutch, but:1) Check the bolts that connect the bellhousing to the engine and the transmission to the bellhousing.
2) Check the u-joints for wear.
3) Thoroughly check the driveshaft assembly, axles, engine and transmission mounts, driveline angles. In rare cases a problem with the transmission or differential internals could cause the vibration.
If the vibration also occurs when the vehicle is stopped and in neutral, it’s either the clutch or the engine:
1) The engine may be misfiring, check for a dead cylinder or other internal problem.
2) If the problem is from excessive crankshaft endplay, the vibration will go away when you disengage the clutch.
3) Check the bolts that connect the bellhousing to the engine and the transmission to the bellhousing.
4) Check the pressure plate and flywheel bolts are torqued down properly.
5) If you’ve verified it’s not the engine or fasteners, it could be either the flywheel or the pressure plate are out of balance. This is more likely if the parts are brand new or recently resurfaced. A serious unbalance after long use is slight.
Johanson, C., & Duffy, J. E. (2010). Manual Drive Trains and Axles. Tinley Park, IL: Goodheart-Willcox Co