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Discussion Starter #1
Another issue that I am dealing with. I R&R'd the transmission and transfer case because I had a very loud noise for a time that I believed was an issue with the pilot bearing.
Once open I found no remains of the pilot bearing and the input shaft was wobbly. I ended up replacing quite a bit more than I originally expected. since my truck was at the 200K mile mark I decided to replace the clutch and pressure plate as well. I chose a SPEC clutch assembly.
Now the issue, from the beginning the clutch operated very strangely. Grabbed at different engagement points. So, what I mean is that as soon as you started to lift your foot it would grab and the vehicle would start moving. Other times it would engage at a normal point, roughly 1/2 way through the clutch pedal travel. Other times I could not disengage the clutch. Foot is hard on the floor and engine is lugging and I cannot put the shifter from gear. I had to stop the engine and put in neutral and restart the engine.
So, SPEC said was issue with clutch hydraulics. I thought so too. I flushed all of the fluid and bled very thoroughly. No change. Next I replaced all of the hydraulic components. Still no change. Now I am suspecting the clutch assembly. SPEC hemed and hawed but agreed to RMA. After inspection returned that same assembly to me as operating normally within specifications. Reinstall and same issues. SPEC continues to blame hydraulic system. Asked SPEC to return and refund and was asked why I think this is SPEC's problem?
Any ideas? I was not having any issues prior to installing the new clutch. No grabbing, chattering, or grinding.
I will never purchase a SPEC product again. Support has not been helpful.:mad:

Sorry about the novel.
 

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I'd like to see verification that the clutch release arm (as observed at the slave piston stick-out rod) is moving in and out in conjunction with your reported clutch issues.

That will confirm hydraulic turned mechanical (outside of the bell-housing) actuation, satisfactory or not.
 

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Recently diagnosed a similar issue to a leaky (internal M/Cx3). Do the verification and confirm correct actuation of slave.

....Philip
 

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Discussion Starter #4
The actuator arm moves fully from rest [resting against the near edge of the opening] to the opposite side until firmly against the further edge of the opening. Each time. I have never seen it not make a full stroke. Also if the pedal is held down I have not seen it move back to rest unless the pedal is released.

I was wondering if the flywheel is a single flat surface or whether the friction surface is a different level from the pressure plate surface. I have noticed a couple of clutch manufacturers specifying +.20 and others nothing at all.

I really appreciate your responses.

Thank you,
 

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So we can confirm that the exposed end of the clutch arm cycles back and forth as designed then. We can only assume the the remainder of the arm inside does as well, unless cracked , bent, or is flexing due to damage. That or the release bearing or arm fingers have issues. Was the arm and bearing inspected and found to be still serviceable earlier?

I was wondering if the flywheel is a single flat surface or whether the friction surface is a different level from the pressure plate surface. I have noticed a couple of clutch manufacturers specifying +.20 and others nothing at all.
I'm not sure if I understand the question. Are you asking if the clutch disc rides on the flywheel in a shouldered recess, a totally flat flywheel surface or on a raised portion of the flywheel? I don't know the answer to that, FWIW. I assume it is totally flat.

What point are you getting at with regards to this .20" dimension? :huh:
 

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Discussion Starter #6
The Release bearing is new from clutch kit and moves freely. The arm appears fine. As far as the +.20 ...My guess is that if there is supposed to be a difference of +.20 between the mounting surface of the pressure plate and the friction surface and the flywheel does not have that or the difference is out of spec then the clutch action would be affected. I had it resurfaced at a NAPA machine shop and never noticed any difference but the grab was considerably less after resurfacing.
 

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Well all I can say is that based on this...
from the beginning the clutch operated very strangely. Grabbed at different engagement points. So, what I mean is that as soon as you started to lift your foot it would grab and the vehicle would start moving. Other times it would engage at a normal point, roughly 1/2 way through the clutch pedal travel. Other times I could not disengage the clutch. Foot is hard on the floor and engine is lugging and I cannot put the shifter from gear. I had to stop the engine and put in neutral and restart the engine.
Then it is an hydraulics issue, UNLESS you can confirm beyond a shadow of a doubt that when those issues occur, the clutch arm IS in fact moving normally. IF it is, then it has to be an internal / mechanical problem.

My gut says it's hydraulic. :rolleyes:
 

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Discussion Starter #8
That is what I thought as well except I did not have this issue prior to replacing the clutch and I did not open the hydraulic system at all. The entire system has been replaced including the lines and my mechanic and a transmission specialty shop both independently both verified that the hydraulics were installed correctly and operated correctly.
The thing is that hydraulics do not offer variable operation. Even with air in the line. So the air compresses and you have partial stroke but not a full stroke and then fade. If the system was leaking then maybe I see some variability. I watched it for probably at least 100 cycles and never saw a variance, hot or cold.
This also would not explain the improvement in the action after the flywheel was re-surfaced.
I am stumped. I have never experienced anything like this or heard of it either. This is not my first clutch job. I usually find in troubleshooting issues that the first question is what was changed between proper operation and now? If the only change is a new part then I suspect that part. I was thrown off by the variable nature of the symptoms.
 

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I'm with you on the oddity that surrounds this whole mess. :(

My thoughts go back to the initial findings of the pilot bearing demise and trans input shaft deterioration. I can't help but think that something was amiss from there, although I can't put my finger on it. Gross misalignment causing (now) improper mechanical movement of the clutch workings? :confused: But why?

Misaligned bell housing to engine mounting (missing dowel pin locators)?

A botched bell housing repair (evidence of which should be obvious)?

Bent or broken clutch arm?

A newly purchased but damaged / poorly manufactured pressure plate and disc?

An improper (binding) fit btwn the clutch disk and trans input shaft splines?
 

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The varying engagement point suggests an actuator related issue - I've seen this on cable type clutches with defective cables, and you might think that since the physical length of the cable doesn't change, that it can't happen, but a binding clutch cable will do that.

Now you have a hydraulic clutch, so let's forget about clutch cables - you seem to think that air in the hydraulics would not cause it to be variable - I disagree.

What I really want to do though is show you something else - a different part of the actuating mechanism ...





The first two pictures are the clutch fork, so to speak, face up & face down - nothing out of the ordinary



This third picture is a close up of the pivot area - taken with a light behind the clutch fork - now you can see the crack, and at around the 10:00 o'clock position - that is a hole, what you're seeing is the light shining through a 1/8" thick piece of steel - the crack extends from the hole to the left of the pivot in the first two pictures, and branches where you see it in the pivot area and extends into the two arms of the fork.

I know you said your fork looks fine - how closely did you look at it - that one looks fine until you get a light behind it.

You'll have to drop the transmission again to determine if you have a similar issue, but I understand it's quite common - oh - this clutch fork has less than 90,000 miles on it - but they're what we call short miles, or city miles - so a lot of stop/start & gear changes.
 

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Discussion Starter #11
Fordem,
Thank you. I did inspect the fork but probably not close enough. I was mostly looking at whether it was straight for showed evidence of flex. I will be pulling the transmission again soon and will be thoroughly inspecting each piece. I have a new clutch and I am looking for a new fork. Since 'dealer' parts are getting difficult to source I want to have everything before I start. My only vehicle as well so ...
 

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Discussion Starter #12
Oh, by the way the transmission shop told me my transmission was on the edge of failure and rebuilt it including re-sleeving the input shaft due to the wear of the 'missing' pilot bearing, replacing all bearings, synchros, and sliders.
 
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