I'm having some refreshment work done to my 94 coupe. While the work was being done, it was determined that it might be a good idea to replace the clutch. So, a new clutch kit (all the typical associated parts) was installed. However, a "rattle/scratching" appeared after installation and after much searching, it has been determined that the thrust bearing is causing the rattling/scratching sound. This sound only occurs when the clutch pedal is pressed to the floor - which I'm not in the habit of doing. This discovery lead to the determination that the crank probably has been harmed and that lead to a replacement engine being recommended. I declined because I'm not sure I want to invest another several thousand dollars in my Vette at this time. Has anyone else had a similar experience? Can an estimate be given as to the life expectancy of my engine by driving it with a bad thrust bearing? Are there signs to be looking for?
Before taking the Vette in for this work to be done, I didn't notice any "rattle" sounds. However, there is a very slight leak of oil from the rear of the oil pan but it is so slight, that only about a third of a quart is lost over 2,000 to 3,000 miles. I really didn't think that was worth doing anything. Any thoughts would be appreciated.

 

It sounds like you have likely a problem with the clutch "release" bearing and certainly NOT the crank-shaft thrust bearing. Regarding your oil leak, that would be the rear main seal likely and I'm somewhat surprised that it wasn't a suggested replacement when the clutch was done. In most higher mileage situations it would be either recommended or suggested. You haven't mentioned your miles.

If you paid retail for the clutch parts and the labor and the release bearing is at fault I would certainly believe the replacement of it would be a covered repair by the shop through the vendor of the clutch and "associated" parts. You need to maybe specify what parts were actually replaced. If you supplied the parts and the shop replaced what you handed them then it's likely you'll pay the second install fee with maybe some consideration.

If the car is driving presently I'd maybe take the repair bill and the parts invoice and have another shop do a drive of your car for diagnostics. What brand and part numbered clutch and parts were used.

 

 

Thanks for your response. I haven't gotten the car back yet and I don't know the brand of clutch purchased by the shop doing the work. The parts installed are: the clutch disc, pressure plate, and throw out, pilot bearing. I placed trust in this shop because of recommendations and reputation. The mechanic doing the work is part owner of the shop and he has assured me everything is according to spec and are in accord with requirements of the dual mass flywheel.
The Vette has just over 85,000 miles on it.
Thanks again, Rick

 

Thanks for your response. Please see my response to WVZR1

 

Its not the thrust bearing
Happens only when he puts the clutch pedal in?

If its the pilot bushing it will squeal and be hard to get in gear.

Ck to make sure he has the right throwout bearing in it and the system is bled

 

If your mechanic thinks it is the thrust bearing, ask him what the crankshaft endplay is.

 

I'm just going to throw this out there. If the noise only appears when the clutch pedal is fully depressed, it could very well being the clutch fork rubbing against the pressure plate. This can be caused either by a worn pivot stud, or if the mechanic didn't fully torque the stud to 28ft/lb. There is also a backing plate on the stud which is vital. It is torqued to only 11 ft/lb and can snap very easily.

Also depends on what parts were used for the clutch repair. The current listing of replacement parts may include the recommended flywheel change. This would be a heavy single mass flywheel which would cause gear rattle. However, this rattle should stop once the clutch pedal is pressed.

 

I agree it sounds like the clutch fork is hitting the pressure plate.

I would recommend that you ask the shop to verify the pressure plate it correct. The reason I recommend this is the last time I changed the clutch on my 93 I was in too big of a hurry and got a clutch kit from Autozone. The kit had the wrong pressure plate. It was too thick, and was impossible to get the clutch fork clear it.

 

Something else I've seen a few times is the pressure plate fingers hitting the flywheel bolts. Usually from a resurfaced flywheel or the wrong bolts and/or washers.

 

I would like to know who the clutch manufacture of your clutch accessories is and where did you purchase these items from also did you replace your flywheel to?
I'm preparing to replace the clutch unit in my 94 C4 vette so your input would be a source of invaluable information.
thanks boonie

 

Sorry for not responding sooner. I didn't purchase the parts. The shop doing the work purchased all the components. There was a question/recommendation to make sure everything matched up and in fact there was a problem with the first set which was returned and a second set replaced it. I've been assured everything is now installed to spec.
Some things to be watchful for - I stayed with my original dual mass flywheel. I'm advised that the conversion away from the dual mass may result in noise from the flywheel/ clutch area. I don't know if that is factual but my flywheel was good and I don't drive all that hard, so there was no reason for me to change.
I'm not the original owner of the car. So, I can't speak to all of it's history. However, for what ever reason studs broke during the disassembly of the transmission and clutch. The result is that the broken studs had to be drilled out, tapped, and new studs installed. I mention this so you can be prepared for the problem and possible additional costs.
I just got the car home and it drives fine. As would be expected, the new clutch grabs in a different place so I'm still getting used to it. I've not experienced any rattle or other issues that I was warned might occur. The mechanic did limit the travel of the clutch pedal so it doesn't go all of the way to the floor - which for me is okay because I rarely would have pushed it all the way down anyway.
One other thing to be aware of and I've mentioned it before. The clutch fork pivot stud and retainer broke and a replacement was hard to find. Thanks to help from Corvette Forum Power Torque Systems was found and the part was found and ordered from them.
I hope my response has been helpful. I thank everyone for their thoughts and suggestions.
Rick