How to tell clutch needs replaced?

BigClay

BigClay

Knower of useless ZJ things
Joined
Sep 24, 2008
Location
Winston-Salem
What are the best ways to tell if a clutch needs to be replaced with out actually cracking open the transmission? Smell? Coasting, engaging the clutch, and watch RPMs? Or...
 
When you let the clutch out & you are in first gear, car no move... :lol:


slipping under throttle, listen to the engine or watch the tach. Hard to get in gear.
 
yep..from my experience it will go thru the following sequence: usually starts slipping initially in high gear..then it will be hard to get in gear..then you may hear squealing of the pilot bushing and then it wont do nuthin'
 
With the vehicle stopped, put it in gear and set the park brake and drive. If it stalls then your clutch is ok, if it slips...well then it's bad. The fact that you are asking tells me it is probably bad and needs to be replaced..
 
No one mentioned adjusting it. Or, is it a hydraulic that has no adjustment? Also, you should have 2-3 inches of free travel on the pedal, from where you start to push it down, to where you feel it hit pressure. If the pedal comes all the way out & still has pressure against it, your either out of adjustment, or Worn out. That will also burn out the release bearing.
 
Yes hyd clutches need no adjusting.

Pedal free play is a good thing. If it releases right at the top, significant wear or you have master/slave problems (bedroom excluded for obvious reasons). Like others mentioned usually 2,3,4 will slip on a grade before it starts to completely fail, usually under a heavier load. If I do a clutch, machine flywheel, replace clutch disc, pressure plate, throwout, pilot and slave if it's internal for sure. Every time if it is internal slave. Even if the slave didn't leak. It will leak in short order if it is internal with integral release bearing. (Learned that once the hard way) $70-$100 is cheap compared to labor to do it again. Or time if you do it yourself. Master at least can be replaced without pulling the trans. Same for external slave.
 
This has stuck with me for years.

If you have shifting problems with the engine on, but not off - you have a clutch problem.

If you have shifting problems with the engine off - you have a transmission problem.

The most notable is the clutch will slip and cause grinding shifting into gears. You can determine synchro issues if the grinding disappears when you double clutch.
 
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ckruzer said:
This has stuck with me for years.

If you have shifting problems with the engine on, but not off - you have a clutch problem.

If you have shifting problems with the engine off - you have a transmission problem.

The most notable is the clutch will slip and cause grinding shifting into gears. You can eliminate synchro issues if the grinding disappears when you double clutch.
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Close.

A slipping clutch won't make it hard to shift, it will slip.

A faulty clutch master or slave cylinder will make it hard to shift with engine on or off. But also could have air in hydraulic system. Another symptom would be clutch will not fully disengage between engine and trans.

This is seen by stopping on flat ground, push in clutch, put in 1st gear, and let off brake, if vehicle creeps forward, it's not fully disengaging.

If the trans won't shift with engine running, and won't disengage trans from engine, the pilot bearing could be shot, crushed on install, or the disc itself could be installed backwards.

If disc is worn badly or glazed over, it will slip under load.
 
A slipping clutch will make it hard to shift, in the sense that because it is slipping your gears are grinding and quickly toasting synchros causing it to be even more difficult.
^ wrong. ur right on that. sorry - was thinking of a failing diaphragm spring.

When looking for transmission issues, you're not using the clutch to shift with the engine off. You simply shift between gears. There is no load.
 
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ckruzer said:
A slipping clutch will make it hard to shift, in the sense that because it is slipping your gears are grinding and quickly toasting synchros causing it to be even more difficult.

When looking for transmission issues, you're not using the clutch to shift with the engine off. You simply shift between gears. There is no load.
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No. A slipping clutch will not cause poor shifting.

that's bad advice to judge shifting quality with clutch out, and engine off. The synchronizers and keys operate on a taper and against pointed D shaped teeth. If they aren't lined up, the trans can be hard to shift while nothing is spinning, and everything is working correctly.

If you have the clutch depressed this will take any load off the input shaft allowing things to rotate into alignment while shifting with engine off.

A slipping clutch will not cause any shifting issues.
 
youre right. sorry, in my mind i was thinking of a failing diaphragm spring. if the spring is failing the load isnt getting removed, and therefore the tran speed is not slowing and the synchros cant help. youre going to be grinding into gear everytime, toasting the syncrhos, unless youre shifting right at the opportune moment where speeds match.

it is not bad advice, is a common method in any transmission shop and have had several shops inform me of this. but that doesnt mean they are right either. ill search some more to back that up :)

Clutch is for slowing the tran speed and removing the load.

Here is a great video for how your clutch stops the transmission input shaft.


Here you can see how the syncrho works. it is independent of the gear. When your shift fork pushes it slides in with the synchro, and allows it to line up with the gear synchro cone.
 
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oops. my bad. not slipping clutch. thats wrong. dont know what i was thinking. in my head i was thinking of a failing diaphragm spring. fixed the above post.
 
ckruzer said:
oops. my bad. not slipping clutch. thats wrong. dont know what i was thinking. in my head i was thinking of a failing diaphragm spring. fixed the above post.
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I was more wondering why you have a flex plate mixed together with a clutch, where you would actually have a flywheel instead (flex plate is for an auto trans). I assume you're actually talking about a pressure plate, especially after mentioning a diaphragm spring?
 
Fabrik8 said:
I was more wondering why you have a flex plate mixed together with a clutch, where you would actually have a flywheel instead (flex plate is for an auto trans). I assume you're actually talking about a pressure plate, especially after mentioning a diaphragm spring?
Click to expand...

Yes. I corrected the post.
 
I always put the vehicle in a higher gear, 3-4, from a dead stop. Then ease clutch out and give it ample throttle to keep from stalling. Slipping clutch would show because of the load. Good clutch would let vehicle creep foward

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