Clutch trouble shooting

dthompson

dthompson

Registered User
Im looking for ideas to help trouble shoot what I now believe to be a clutch problem. For a while now, I have experienced a problem in the following scenario: The engine is cold, I press in the clutch and start the car, put the car in rev, back out of the garage, release the clutch and then let the car warm up in the drive way in neutral with the clutch out. I let the car partially warm up for a few minutes, then push the clutch in and try to put it in 1st, but its like im blocked out of the gear... i try all the other gears and its the same thing. pumping the clutch a dozen times makes no difference. if i push hard enough, it will eventually go into gear. or if i shut the engine off (while still holding the clutch in, it will fall into gear as soon as the engine stops spinning. i can easily shift into all gears while the engine is off. Otherwise the car drives perfectly fine. shifts fine while you are rolling and normal driving.

What I am working with: Stock resurfaced flywheel (89 sc), Centerforce DF clutch with about 4k miles, aftermarket replacement slave cylinder (centric brand i think), aftermarket replacement hydraulic line, and stock original master cylinder.

These are the things that i have tried and/or tested:

Ive replaced blockers with Mike Pucket's CF blockers and tried all kinds of fluids. I thought maybe it was a fluid problem with the blockers that i just could not get right, so i pulled the trans and replaced the blockers with solid brass blockers. i still have the same problem.

I have replaced the pilot bearing. Same problem.

I inspected the clutch flywheel and PP. there are some slight discolored spots on the PP. I held a straight edge across the mounting surface of the PP and measured down to the friction surface using calipers and it seemed to be parallel within a few thousandths everywhere a checked. I held a straight edge across the friction surface of the PP and it seemed flat except for one spot that i could fit a 0.006" feeler gauge under the straight edge. The clutch disk looked ok to me, i did not see anything physically wrong with the springs and the splines moved easily on the input shaft. The flywheel seemed flat and parallel to the transmission mating surface of the block using using the same method of measurements described in checking the PP.

PP.jpg
pp2.jpg
fly2.jpg
disk1.jpg
disk2.jpg

I used my cell phone to capture video of the slave cylinder pushing on the PP to verify that the hydraulic system was working visually. The slave seems to be traveling 3/4" it looks like to me. The clutch disengages near the top of the pedal, so it seems to me that the hydraulic system is functioning properly. I repaired the clutch pedal linkage recently securing the piston rod to the pedal using a shoulder bolt.


So that is where I am at right now. It seems like the input shaft is spinning which may be causing this problem, but i dont know how to prove it. I feel like I am stuck other than throwing parts at it which is now going to be expensive. If anyone has suggestions on what to try, test, measure, or replace... I am all ears. New flywheels and clutches are expensive, so if thats what I need, then I want to make sure I diagnose it properly. Plus every time i have to pull this trans out, I am rolling around on the concrete which is taking a toll on my body.

Thanks,
Derek
 
Last edited:
more pictures of flywheel and input shaft.

fly1.jpg
fly3.jpg
input.jpg

the arrows on the input shaft are highlighting shiny areas on the splines where you can see the disk was sliding.

Thanks,
Derek
 
Good evening


I experience the similar symptoms. The problem deteriorated to the point I would have the car start and idle for at least 40 minutes before I could get the transmission to engage in reverse and


first. I ordered a clutch kit, the shifter rebuild kit, the clutch peddle bushing, the master and the clutch line. After adding friction modifier, ATF change and clutch bleed the transmission shifted


great with the exception of first gear because of all the "hulk smash" I did to put it in gear. I suspect the problem might be a leaking master and or clutch line issue if there is not issue


with the flywheel machined limits.



Good Luck.
 
KMT said:
I see:

...but I don't see the word 'shim' anywhere?
Click to expand...

i have not removed the flywheel to see if they shimmed behind it? The engine builder installed the flywheel and the clutch when i had it built. there are no shims behind the slave.

I'm guessing that you are getting at the idea the clutch is too far away from the flywheel because it was resurfaced and therefore not pressing on the clutch enough to release it fully. My assumption is that the slave is moving enough to disengage the clutch because the clutch engages at top of the pedal travel. I would say it engages at .75" of pedal travel if the overall pedal travel is ~3". also combining this with the video, this doesnt seem like the problem to me. But I could be wrong, Im not a mechanic. I've still got a lot to learn.
 
Measured the distance on that install from the block mounting surface to the face of the friction surface on the flywheel yet?

I'll try to find the spec - apparently it doesn't take much to cause grief. Maybe as little as a thousandth inch...
 
Good morning

Post#1 picture attachment #2 and Post #2 picture attachment #1 the pilot bearing does not look fully installed. Maybe angle of the camera?
 
sam jones said:
Good morning

Post#1 picture attachment #2 and Post #2 picture attachment #1 the pilot bearing does not look fully installed. Maybe angle of the camera?
Click to expand...

I think it is installed correctly. the pilot is comprised of an outer bushing and an inner needle bearing. the outer bushing is installed flush and the need bearing protrudes about 0.1". I used a national bearing brand, but this is a picture of the timken brand. Also notice the witness marks on the input shaft. their are no marks on near where the splines begin.

pilot.jpg
pilot 2.jpg
 
dthompson said:
Thanks Dave. How do I check it to prove that it is bad other than swap and test?
Click to expand...
I don't think you could really do a reliable test/check. But your symptoms are 99% bad disc. Since everything else is good, I'd just order a new disc.
 
I mean, of course I'm qualifying this with the understanding that the system is properly bled and the pedal pin engagement is correct such that your pedal free play is within spec and that the clutch is engaging within a reasonable range of the middle of pedal travel. These are mechanical adjustments/parameters that are assumed to be correct at this point.
 
XR7 Dave said:
I mean, of course I'm qualifying this with the understanding that the system is properly bled and the pedal pin engagement is correct such that your pedal free play is within spec and that the clutch is engaging within a reasonable range of the middle of pedal travel. These are mechanical adjustments/parameters that are assumed to be correct at this point.
Click to expand...

It feels like it is bled correctly, the pedal feels pretty firm and consistent as you push it. the clutch pedal pin has been replaced by a shoulder bolt and bronze bushing. I have no idea what the free play spec is, but I would describe it as very little. I would describe the clutch engagement as within the top 25% of pedal travel. I made this video tonight to show you just in case I'm not describing it correctly.

showing how I modified the clutch pedal attachment
20161229_114904.jpg

video showing free play and clutch engagement. if you turn the volume up enough you can hear the engine load as the clutch engages at the same time I say "engaging". lol you can also hear me grunt as i try to put it back into first gear!

Thanks,
Derek
 
I could not find a spec on flywheel thickness. The only thing i found was that you need to use a new flywheel if you have to machine more than 0.045" off of it. that is not particular helpful if you dont know where it started. I assume that as long as it is not running out it is ok since the clutch engages so high on the pedal.

I also bought a dial gauge and magnetic base today. I will be able to check fly wheel run out and to see if the input shaft is bent/runout.

Is there a spec for flywheel runout? i did not see that in the shop manual.
 
I got my flywheel from Mike puckett. He gave me the thickness of the flywheel but all mine needed was a shim between the crank and flywheel.
 
I measured the flywheel thickness this afternoon. It measures 0.962" thick

I need to check the runout again. My setup was not rigid enough and the video was not clear (i cant see dial while I turn the crank). It looks like it was less than the 0.007" listed in the other thread... if that really is the spec.
 
The flywheel runout is less than 0.001"

I set the dial gauge up on the input shaft and im not sure if its bent or if is just a result of the tapered bearings. It runs out about 0.015" and wiggling it by hand it looks like 0.020"-0.030" depending on force. If I had to guess, I would think this is normal given the bearing structure. Its not going to move like this when it is in the pilot bearing. But I will post it and you guys can correct me if I am wrong. Check out the video (i apologize for the poor lighting and video quality)...


The transmission was rebuilt using all original factory parts except the blockers, seals, main and countershaft nuts, and tailshaft bushing. No shims were added to the input shaft. The last time i had it apart i checked the dimensions per the service manual and it is super close to the correct tolerance on the input shaft shim. Although that stuff is somewhat tricky to measure.

Thanks,
Derek
 
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