New engine and clutch, have weird vibration @3K RPM

Question

I just replaced (well, had someone else replace) the engine in my 06 Solstice.

The engine runs great for the most part (will open a separate question about that), but there is a weird vibration at about 3K RPM. The vibration disappears when the clutch is disengaged (? pedal down == disengaged, I think). It appears to be RPM-dependent, not speed dependent, which is weird since it stops if the clutch is disengaged.

Other potentially-relevant data:

1. New Spec stage 2 clutch, pilot bearing, etc.
2. Re-used flywheel from previous engine. It's a Spec aluminum flywheel with about 2k miles on it. It worked fine in the previous install (same car).
3. Engine seems strong and smooth - it revs fine, etc.
4. Probably a different problem: there's a weird rubbing/grinding feel when the wheels are turned to the right. I notice it most when backing out of a parking space or my driveway. It does not happen when turning left. I thought it might be a wheel bearing, but it only happens when the wheels are turned to the right.

The shop that did the engine install thought it might be a bad transmission mount. They offered to swap it out but I was already several thousand dollars in, and it's not a difficult procedure so I thought I'd do it myself. However, I haven't had the time to jack up the car and have a look.

So, my guess-analysis:

• Engine runs fine otherwise, and the vibration doesn't seem to affect revving, etc.
• If it was coming from behind the transmission (driveshaft, differential, etc.), I would expect it to be speed-dependent, not RPM-dependent.
• Flywheel was good before, can't imagine why it would be out of round.

Possibilities:

• Bad transmission mount
• Bad clutch install (mind you, it works just fine, though it feels as if the slave cylinder isn't pushing quite far enough - can be "notchy" going into gear)
• ???

Suggestions?

Answer 1

Since the issue happens only when the clutch is engaged the problem is not with the engine, flywheel, or pressure plate. Since it isn't speed dependent, but RPM dependent, we can eliminate the drive train behind the transmission. Since your transmission didn't have an issue prior to the clutch install, I believe we can eliminate that as well. The only thing which I believe it could be at this point is an improperly balanced friction disk. Yes, the tranny shop could have done something to the transmission, but from my point of view, that is highly unlikely. While an imbalanced friction disk is highly unlikely, it is not out of the realm of possibility. It could be caused by improper factory balance, a careless mechanic, or a dislodged (out of place) friction puck.

As an aside, while the clutch would be covered under warranty, it is unlikely the labor to install the clutch would be. It is, however, something the shop should have noticed prior to giving the car back to you.