Strange vibration about 5k...

[ammrpm]

Here's some background on the car. I have a 93 ZR-1 I bought about 4 months ago. The car has about 15k miles on it. It had a callaway C.H.I.E.F. package put on it in 95. I believe it has 4.10 gears in it as well. The tires are fairly new, but they may have some flat spots from sitting for a while.

I noticed while driving the car recently that it had a pronounced vibration above 5k rpms that just seemed to get worse the harder I pushed it. After my few runs to 7k rpms I noticed a noise that seemed kind of high pitched. The noise was constant and would increase in volume with rpm of motor.

I got the car home fine. The noise was still there, but the car shifted through the gears no problem and seemed to drive fine at cruising rpm and speeds.

I parked the car and left it running. I opened the hood and listened for the noise. It did not seem to be coming from the engine(thank god!). I got down under the car and it seemed to be coming from the trans/bell housing area.

Well, I put the car up in the air and pulled the inspection plate on the clutch housing. I found what looks like chunks of the friction material stuck between the ring gear and the clutch housing. I believe this is what is causing my noise as the ring gear was just grinding through this material as it spun.

So I figured it was time to pull the trans and do some inspection. This is what I found...

Pressure plate:




Clutch disc:


Flywheel:


Now to my questions...

1. Does anyone know what Pressure plate this is? Is it a centerforce?
2. I noticed that when I turn the TOB it makes some noise. Should these make any noise when you turn them by hand?
3. From the clutch disc picture you can see where one of the pieces of friction material on the disc surface that faces the engine has decided to completely come off. Would just this little bit of material falling off cause the vibration I was feeling about 5k rpms?
4. Does anyone know what type of flywheel this is? I know it is some kind of lightweight flywheel because it only weighs 17lbs. But it does not look like a fidanza.
5. Would this flywheel still be usable if it was cleaned up a bit? Don't want to spend money on a new flywheel if I don't need it.

Thanks for any help!
Aaron

[mike100]

Looks like a Centerforce "Stage II"-ish clutch. They make a stage 1 which is a normal fully faced friction disc with a pressure plate that is like stock, but with the centrifugal weights and a claim of 30 percent more holding power.

aftermarket parts FTL.

ON EDIt: i looked it up- CF has two stages of regular clutch disc and one they call "Dual Friction". That;s what you have and the retail price for that clutch kit is more than a $1000. I'd just get a regular one at half the price. I have had good luck with the CF1 (stage 1) kits on other cars though.

[ammrpm]

Thanks for the quick response Mike!

Anyone else think the clutch disc damage in the picture would cause the vibration I am having?

Does the flywheel still look usable?

Aaron

[Pete]

Looks like a DRM (Doug Rippie) flywheel.
If you post part # it will tell you if it is DRM, if # ends with 80 then it's DRM.

Yes,it can be machined.

Yes,that one clucth piece will cause vibration.

I would take those wieghts off the pressure plate great theory but in reality does not work.
Mike's suggestion is on the money.

If you do have the DRM flywheel and want to sell let me know.

Pete

[ammrpm]

Hi Pete,

Here is the only thing that looked like a part number on the back of the flywheel:

[Pete]

Yeap,DRM flywheel.

If you change the last 2 #'s to 79 without the A, it's an LT1 camaro flywheel.

The differance LT1 has 6 bolts,LT5 has 8

Pete

[-=Jeff=-]

That is the flywheel i would want if i went to Single Mass

[mike100]

Is it just me, or are the centrifugal counterweights pulling the springs the wrong way on a pull type pressure plate? (I know they work right on a standard arrangement)

when you pull back on the t/o bearing, doesn't it release the pressure on the disc?

Whether or not the weights do anything significant on the Centerforce design is debatable, but it seems like the clutches for ZF vettes are probably best left without the gadgets. I will say again that their standard clutch disks and pressure plates are of good quality- I would run one if I found it for a good price.

[ammrpm]

Thanks for the comments everyone!

I think I am going to try and reuse this flywheel.

Would it be ok to just break the glaze off of the flywheel with a scrotch brite pad and reuse it with a new clutch disc/PP/tob? Or does it need to be machined before it can be used again?

[ammrpm]

Just wanted to provide a followup to this thread... well I decided to reuse the DRM flywheel and put in a new Carolina clutch stage 2 kit. Everything went in perfect. The clutch feels great. The only problem is that did not resolve my vibration issue.

So I put it back up in the air. I pulled the driveshaft and sent it out to get checked. Guess what, the driveshaft had a runout of .090 on it. That was my vibration problem. So I had to find a replacement driveshaft.

So after getting another driveshaft, puting in new ujoints and checking the balance on that one. The car runs very smooth now!

Moral of the story: check the driveshaft if you think you have a driveline vibration issue.