while its true the LS7 clutch and pressure plate are zero balanced as a unit, but that unit is used to final balance the rotating mass of the engine.. its done with weights set in the fly wheel... you have to take them out of the original unit and place them exactly where they were in the new flywheel. Sorry I didnt read though all of the posts...
Bill aka ET

 

I spoke with them yeaterday and they said they can't find anythin wrong with it so far. They said they want to look more at the rear diff. The only thing I didn't change on the car is the master cylinder which could be causing the shift problems, but defenitely not vibration. I was pretty sure both problems go hand and hand. Also, if I do a small clutch dunp or if I'm rolling backwards, and let out the clutch in first, I'll get a very loud grind from the clutch area, and the car won't move. Sounds like the pilot bearing? The pilot bearing is new and they say there's nothing wrong with it.

 

QuickC5, you might have an even more serious problem unrelated to the flywheel imbalance; but believe me, the flywheel weight thing so well described by THBWLZ is true to every detail. I experienced it 12 years ago, and have been on the Forum soapbox ever since to try to help others avoid the pain and agony I suffered.
As explained above, if it is the FW weight issue, and you don't have the original FW, then there are two possibilities for re-balancing your driveline. The pro way is to find a shop/dealer with a strobe balancer (as described in the 2000 service manual). The factory rep brought one to my dealer in 1999 and managed to rebalance mine).
The shade-tree way is to open the inspection cover and bang a 1 oz weight into one of the holes in the FW, and drive it. Then move the wt to the next hole and drive it - you get the idea.

Good luck,
DG

 

Replace pilot bearing? Did you have the crank pulley off and put it back how it was?

 

I had the crank pulley off when I replaced it with the tci. Put the new one in with no problem. I had the stock clutch in it for around 1500 miles on it. Did not get any vibration just clutch pedal sticking to the floor at full throttle. I then had the clutch replaced by the stealership. After around 375 miles or so I started getting grinding when shifting especially at high rpms. 100 miles after that came vibration.
I think the shift problems are a fauly master cylinder. I'm going to have it replaced, and the vibration is something entirely different. Although they seem to disapear and reapear together.
What I don't understand is the grinding that comes with a clutch dump. The pilot bearing is new. It seems like it is the pilot bearing even though the shop where it's at now says its fine.

 

A balance issue has not ben ruled out as of yet. But, I think it's unlikely because it disapears. It seems anytime the trans clutch etc are pulled it goes away, but then comes back.

 

quickc5z06 - I've had the exact same problem you're describing ever since I replaced my clutch in 2004 (first an SLP, now a Monster 3). I've noticed that on a cold engine the vibration isn't there but as the engine warms up the vibration progressively gets worse. I also tried leaving the car in 3rd at 3500 RPM when the vibration was the worst and pushed the clutch in and released quickly a few times; I noticed the vibration would vary in intensity and sometimes almost completely go away.

Hope this info helps a little.

 

Check your pilot bearing guys. If you jam that input shaft too hard, it'll eat it up. I experienced this exact same thing after a clutch install. Had to tear it all back down just b/c I wasn't paying attention to that bearing.

 

They are rubber bushings inside the torque tube. Theres one on each end. They are about 100.00 for a pair I believe depending on where you buy them. Heres a link with pics of them

http://forums.corvetteforum.com/c5-t...with-pics.html

However with 17.5K miles i doubt yours are worn/cracked unless your car is heavily modded and drag raced at the track.

 

Got the car back today. The shop pretty much said they are lost to what it can be. Took the trans apart, diff, and inspected the clutch assembly and torque tube. It's definitely better than when I brought it in, but that doesn't mean much, as the problem can all of sudden get severe like it has before.
When I drove it home the severity of the problem changed quite a few times. When the severity of the vibration increases, the shif/grind problem does as well. It's the worst when I downshift to a gear that will bring my rpm up to around 4k+. Or if i stomp on it in first gear. When I stomped it in first, it got pretty bad. It actually vibrated the car harder than i've ever felt. With all that there were periods where I was able to get on it(2nd or third gear) where I had absaloutly no vibration( full throttle) throughout the whole gear, and was able to go into gear right away as smooth as butter( when it's acting up I have to wait a few seconds to shift or else it'll grind).
I'm going to install a new master cylinder next week and see if that helps at all. Whatever it is, it seems like when I get on it something is slipping causing vibration, and when I go to shift whatever it is keeps turning, making it impossible to shift. I notice absaloutly no spikes in rpm with torque loss like associated with a slipping clutch.
My knowledge in clutch assemblies and workings are minimal, but I think the problem is somewhere in the input shaft/pilot bearing/crank, even though the shop says they are fine.
Thanks for all the input so far. All help is greatly appreciated.

 

I am having the same problem we replaced the clutch on my 2000 vert at
110,000 miles...clutch was still holding but a little chatter...put in the LS7
kit, new slave, flywheel, pilot bearing and rebuilt the torque tube...car seemed smooth for the first 100 miles....I got on it a little in first and 2nd...it then started the vibration...still vibrates with the clutch depressed....so its got to be the flywheel...let me know of any updates to your situation

I still have the stock flywheel...so maybe I can check that for balance.

 

Does it vibrate at rpm when you are sitting still? If not it is the torque tube...

 

I does vibrate when revving the engine with the clutch depress...its not real bad...but very different than when I had the stock clutch

 

Had entire clutch, flywheel, and hydraulic system replaced and now have a severe vibration around 900 RPM, with and without clutch depressed or transmission engaged. Currently back at the shop but they have no idea how to fix.

 

Tell the shop not to discard your stock components you will need them to rebalance the new setup

 

Yes, have your shop take a look at your stock units. Check around the perimeter in any of the 12 circumferential holes located there and see if there are any holes with weights added into them. Hopefully they are willing to work with you on this. If they have the ability to put your stock FW and PP together and check the state of balance of those, have them do it. Whatever the original combo happens to be with respect to balance, have them make your replacement combo the same. If the original setup is near zero, then have them make the new combo near zero. If the original setup is 12 gram·in imbalanced at some orientation, then make the replacement the same. Then of course it has to go back on the crank in the same orientation as the stock unit did. If it didn't vibrate before the change, then you need to make your replacement combo match what you took out. They might not believe that these engines go through a final balance check and are balanced externally IF NEEDED, but that doesn't change the fact that it is true. Good luck. Still having your original factory FW/PP is the key.

 

Interesting read...
I just did a conversion from an A4 to an MN12. New GM FW, LS6 clutch, PP. I had the FW and PP statically balanced before the install. So far it seems fine. From this post, it seems my engine is within the 1.5 grams spec. Hopefully, since I didn't have a old uniquely balanced FW, PP combo this will stay fine. Fingers crossed.

 

Unfortunately the shop disposed of my original parts, so i may be out of luck.

 

Actually, it means that your engine's internals were less than .5 oz·in, which is good. The factory post assembly balancing takes care of imbalance contributions from the engine internals, FW, and PP all together. You took care of the two, and your internals were ok to begin with. So, from now on, when you change a clutch, you know, you are best off with a zero balanced FW/PP assembly, as you would expect for an internally balanced (by design) engine. Your guess work is done.

 

You're not out of luck, it's just a matter of how much this shop will be willing to work with you. If they have ruled out any other causes of the vibration, like a screwed up pilot bearing, propshaft couplers, mounts, exhaust touching anything, that kind of stuff, then there are ways to balance your engine/clutch assy while still in the car.

What is the state of the car right now? Is the driveline apart and the clutch out of the car? Or is everything together at their shop?