Hello, new to forum and vette. So when in neutral i hear a humming sound which goes away when pedal is pressed, which tells me throwout bearing. Also when in 4th 5th gear clutch is slipping when i give a good amount of throttle. After some research i found the clutch and flywheel have been discontinued. I also found out, installing these conversion kits may create a knock in tranny/engine. I even had a chev dealership refuse to do the work in fear it may come back to haunt them. If anyone can lead me in the right direction i would appreciate the help! Just want my car fixed properly.

 

If the sound goes away when the pedal is pressed then it is not the throw out bearing. If it starts to make a noise when the clutch pedal IS pressed then it is the throw out bearing. Mine makes a faint "whirl" in neutral as well without the clutch pressed in. Most of them do it, especially the black tag ZF6's. My 94' has the black tag, yours might as well.

 

thanks for the reply, do u have any advise for the slipping in 4th 5th 6th gear when given extra throttle?

 

Sounds like a worn friction disc. Probably will need to pull the trans and bell housing to have a look. Good time to get yourself a factory service manual.

 

Thanks again. If i need to replace this clutch/flywheel do you know the best route due to the discontinued parts? I've heard the stories of a knock with these aftermarket parts but i see no other alternative.

 

No worries. I don't have his number but call Jim jandik at power torque systems. He has all the Zf6 clutch NOS parts. I just went with a stock kit from Carolina clutch. Scuffed and cleaned the flywheel with a maroon scotch briute pad an hrew it all back together.

 

Sorry for any spelling issues on a cell phone with fat thumbs

 

thanks so much. I did pull info on carolina clutch the other day. I will not be doing this work myself, so i just want to be sure im putting in quality parts the first time due to labor cost! So i take it you have done this conversion, if so are you happy with it?

 

I don't blame you, changing a C4 ZF6 clutch on jack stands in a garage isn't the most fun thing to do.

I didn't do a conversion per say, just replaced the clutch. I was contemplating on converting to a single mass fly wheel from the dual mass but did not. Also contact Bill Boudreau (ZF Doc) for more info. He informed me that the OEM pressure plates are built to last for 1,000,000 cycles, whereas chinese replacements that were tested only lasted 100,000 cycles (every aftermarket pressure plate including carolina clutch). He actually told me even with 105,000 miles to re use the original pressure plate, fly wheel, and throw out bearing. I went ahead and saved the pressure plate and throw out bearing and put it in a box just for safe keeping. I went ahead and used a stock replacement kit from Carolina Clutch, I believe it was around $350. It includes the pressure plate, friction disc, throw out bearing, pilot bearing, and alignment tool. I have had it for about 6-7000 miles now and so far so good. Definitely grabs harder, transmission is still noisy, and the clutch still doesn't engage until almost at the top of the pedal travel (I am told this is also normal). All in all I am satisfied. I drive the car everyday and sometimes it can be interesting but it does the job well.

FYI- my clutch was beginning to slip in 3rd, 4th, and 5th at low rpms with a lot of load like you are describing. Here is what my friction disc looked like:



All the clutch dust inside the bell housing:




Flywheel:



Flywheel after maroon scotch brite cleaning:





All in all everything cleaned up and worked out well. For the original clutch to hold up to 105,000 miles is pretty astonishing to me, especially on a Corvette that is driven pretty hard.

 

I can state I went through the came aas TorchTarga94. I got the same stuff from Carolina clutch and ha it replaced. Cost total w/ labor round $800. I live on LI NY. After replacement I did have a little chatter in the clutch for awhile but that works it's way out as the parts wear in together. Few thousand miles on the new tranny and all is good. That hum you get in neutral seems to be normal. I have the same

 

My Corvette shop replaced my dual mass with a Carolina single mass.

Now it rattles through first and second gears and when going slow in 5th or 6th gear.

Terrible to have a cool looking car that sounds like Jed Clampett's truck....

Rebuild the dual mass or find a dual mass.