Ed K

Hey Guys,

97 Z28 here that just had clutch fork, and (aftermarket) clutch assembly (pp, bearing, clutch plate, orig flywheel but resurfaced) replaced at the dealer.

Appears I now have a high RPM vibration, around 4.5 - 5k, in all gears. No strange noises or other problems...just this vib at high RPM.

What are your thoughts about what is causing this? Appears to have started after this clutch install.

Thanks,

Ed

Injuneer

Sounds like the clutch assembly balance wasn't checked.

Ed K

Thanks Fred.

Since the LT1 is a externally balanced motor, and the original flywheel was resurfaced, how does one properly balance everything?

Also, could it be the tech just put the FW back nine wrong position? Is there anyway to determine what the original position was if the tech did not put alignment marks?

Injuneer

If you never had a vibration problem before, the engine/FW is most likely properly balanced. I guess it's possible they did something to alter the balance of the flywheel when they resurfaced it. If the balance weight was removed, it would probably shake at much lower RPM. There's an index pin, so the FW has to be in the correct position.

That leaves the clutch assembly. That doesn't have to be balanced with the engine rotating assembly. But given the mass of the pressure plate and disc, each has to be neutral balanced by itself. I would assume a quality pressure plate and a quality disc would have been checked for balance at the factory, but given the extensive use of imported replacement parts, who knows?

What does the shop that installed the clutch have to say?

Ed K

Oh, thanks Fred, there's an index pin...interesting...

It's at the shop now, tech has not looked at it yet. Although it appears they think it's unlikely to be a balance issue...will advise what they report...might be a few days since they are pretty busy.

Ed K

Tech has checked all motor, bolt and connections point, and problem is still there. He's recorded the vibration and sent it to GM for their input prior to opening everything back up again.

4586

My .02..Check the U-joint caps, are they seated fully, roller bearings missing inside caps..