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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?

  • If I read you correctly, you are saying if the clutch pedal is down (clutch disengaged) the vibration goes away even if you run the engine up to the redline? (BTW - Great details! Love your questions. I wish more people would ask the questions the same way.) – Pᴀᴜʟsᴛᴇʀ2 Sep 24 '15 at 21:12
  • @Paulster2 Thanks! I do what I can. :) Yes, the noise disappears with clutch disengaged, revving all the way through redline. Starting to wonder if the transmission was somehow damaged. Bent input shaft? But then it'd go nuts all the time, :( – 3Dave Sep 24 '15 at 21:38
  • Is the noise there in neutral, with the clutch engaged? Or only while you're driving (in gear)? – Shamtam Sep 25 '15 at 14:42
  • @Shamtam only when driving / in gear. – 3Dave Sep 27 '15 at 15:24
  • @DavidLively Great question. Writing and format. :) – DucatiKiller Dec 14 '15 at 23:43
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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.

  • It's worth mentioning that the flywheel should have been resurfaced during the swap. If it wasn't, I imagine it could cause some balance issues with the break-in of the new clutch disc. – Shamtam Sep 24 '15 at 23:30
  • @Shamtam - I believe the Spec aluminum flywheel has a replaceable friction plate where the disk rides. You just have to replace the plate to get a new surface. With only 2k miles on it, I doubt it even shows any signs of wear. Probably could have used some burnishing, though. – Pᴀᴜʟsᴛᴇʀ2 Sep 24 '15 at 23:58
  • Good to know, I'd never seen that before. However, with the new information that this only happens when in gear (and not in neutral), I don't see how it would be an imbalanced friction disk, since that would cause this vibration when the gearbox is in neutral as well. Sounds like it's transmission related. – Shamtam Sep 27 '15 at 18:37
  • Well, engine #3 just exploded. Oil drained from around the head as did the coolant. Yay. – 3Dave Nov 6 '15 at 19:57
  • Well, that sux. – Pᴀᴜʟsᴛᴇʀ2 Nov 6 '15 at 20:04

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