Think My Pilot Bearing Is Fried... - Pontiac GTO Forum
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post #1 of 12 (permalink) Old 11-29-2015, 09:26 PM Thread Starter
 
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Think My Pilot Bearing Is Fried...

So I swapped out my McLeod Stage 2 clutch for a Monster Stage 3 as well as a new slave roughly 10k miles ago. The car ran, and shifted great up until a few weeks ago when it started slightly grinding between gear shifts and will now sometimes grind when the clutch is disengaged and held. I do not believe a improperly functioning slave is causing the grinding as there is no fluid beneath the trans. The clutch functions, holds, and disengages as it should so I don't believe thats the issue. That leaves the pilot bearing. Since the pilot bearing only in use when the clutch is disengaged, I believe that explains that noise as well as perhaps the pilot bearing is causing friction on the input shaft thereby I think explaining the noise when shifting. If I rev match when I shift I can eliminate the grinding. If it is the pilot bearing, how bad of an idea is it to run it as is? Do my synchros need to be replaced due to the grinding?

Does anybody have any input on this? Would really like to hear somebody else's opinion before I pull the trans.
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post #2 of 12 (permalink) Old 11-30-2015, 03:03 AM
 
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The slave cyl is spring loaded to push the pilot bearing against the pp fingers, and is turning all the time.
It would make some noise all the time if it were bad.
Sounds like bad synchronizers, or air in the hydraulics.

Larry

2005 GTO Quick - 1984 Honda V65 Magna Quicker - 2004 Z06 Quickest
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post #3 of 12 (permalink) Old 11-30-2015, 09:09 AM Thread Starter
 
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Originally Posted by AlaGreyGoat View Post
The slave cyl is spring loaded to push the pilot bearing against the pp fingers, and is turning all the time.
It would make some noise all the time if it were bad.
Sounds like bad synchronizers, or air in the hydraulics.

Larry
The pilot bearing sits within the crankshaft and stabilizes the tip of the input shaft. I believe you're thinking of something else.

But the grinding is the same noise as you would get from air in the hydraulics, except that it also grinds sometimes just sitting and not moving in traffic with the clutch disengaged.
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post #4 of 12 (permalink) Old 11-30-2015, 03:55 PM
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The bearing on the clutch pressure plate is the throw out bearing. Sounds like air in the hydraulic system.
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post #5 of 12 (permalink) Old 11-30-2015, 05:09 PM
 
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Yeah, got the throw out bearing confused with the pilot bearing.
After re reading, could be the throw out or the pilot bearing. If it's the
throw out, it will usually start making a noise at any time.
A bad throw out will eat up the pp fingers, and a bad pilot can damage
the bearing surface, and add undue wear to the input shaft bearing.

Larry

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post #6 of 12 (permalink) Old 12-01-2015, 05:13 PM
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Stop on a flat surface, put car in gear and hold the clutch to the floor with the brakes off then rev it a few times. If the car feels like it wants to move you have a bad slave, very worn clutch, as mentioned air in the line or the slave mounting needs measurement and shimming

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post #7 of 12 (permalink) Old 12-02-2015, 09:50 AM
 
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"and will now sometimes grind when the clutch is disengaged and held"

Can't see any grinding noise being caused by a slave malfunction in this
scenario.

Larry

2005 GTO Quick - 1984 Honda V65 Magna Quicker - 2004 Z06 Quickest
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post #8 of 12 (permalink) Old 12-02-2015, 01:50 PM
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Quote:
Originally Posted by AlaGreyGoat View Post
"and will now sometimes grind when the clutch is disengaged and held"

Can't see any grinding noise being caused by a slave malfunction in this
scenario.

Larry
I'm assuming that he means he can push the clutch in all the way and tries to shift. If the pressure plate fingers aren't being depressed far enough due to air in the system or an improper spacing from the slave/throwout bearing face to the PP fingers it grinds.

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post #9 of 12 (permalink) Old 12-02-2015, 06:27 PM Thread Starter
 
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First of all thanks for the quick responses and feedback guys, it's really much appreciated.

What I mean the clutch is disengaged and held is that say in stop and go traffic, the car is in first gear, and I disengage (push in) the clutch. Sometimes the car will simply grind at any particular time. As soon as I take the tranny out of gear and release and disengage the clutch again, the noise goes away.

As far as shimming, the tranny originally had a shim when the car had a spec stage 2 clutch (not McLeod, sorry typo). However, I had a excellent mechanic who installed the Monster as well as new slave/(comes with new throwout, correct?) who measured slave distance and said the shim was not needed. Additionally on the Monster website it claims no Monster clutches require shims. Also, the setup wasn't doing this for at least several thousand miles so I don't believe it's that.

I also read it is possible that the slave can push the pp too far causing it to grind on the flywheel, but I don't believe that would also explain the tranny shifting noise as well.

I just tried putting it in gear and revving the engine but got nothing. Rev'd it to 4k 3 or 4 times and got nothing, car did not move forward one bit.

If the pilot bearing doesn't make noise when fried and the clutch setup is good, the only thing I could think of is the tranny is shot. However, I couldn't begin to think why the tranny would make noise when not engaged by the clutch and sitting at a stop in traffic, plus it had a stage 2 (or 3?) rebuild by a professional shop 55kish miles ago.
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post #10 of 12 (permalink) Old 12-04-2015, 08:55 AM
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Under an engaged clutch (pedal released) the transmission input shaft and pilot bearing are both turning the same. When the clutch pedal is pressed down and the shifter is in neutral or the car is not moving the input shaft is stationary and the crank/flywheel is turning. The pilot bearing is in effect then and if that's when you're hearing it it is probably bad. Usually the pilot bearing is replaced when the clutch is as it's cheap insurance but it sounds like it wasn't. If it's bad it can chew up your input shaft and be an expensive repair. I'd get it looked at ASAP

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