Driveline vibration at low RPM after clutch swap

[johunn]

After the clutch was swapped on my 2014 manual BRZ, the car now has vibrations at low RPM under acceleration that multiple posters have mentioned in other threads. Basically the issue appears when accelerating in the 1700-1900 RPM range in any gear apart from the first. The whole car is vibrating and there is a rattling sound coming from the gearbox area. I am wondering if anyone has finally found a solution to the issue or you just live with it?

Some posters have commented that this is how the twins work. Well that is most definitely not the case, because prior to the swap there were no such issues and it worked perfectly fine accelerating from any RPM. Some posters have mentioned that "lugging" the car is not good. Once again, it's not like I am always driving at 1700 RPM. There are multiple real world scenarios where the car is at the abovementioned RPM and there is no point in swapping down a gear. For example going over a speedbump at 10-15kph, I am not going to swap down a gear from second to first. Slowing down in traffic to 40kph and slowly picking up speed, once again not going down from third to second, it's not like I am trying to race somewhere. All of these scenarios were never before a problem for the BRZ, it picked up speed without any issues and rattles and it has never been a problem for any of the other cars I've driven.

The car is totally stock and has done 78 000km. The new clutch is an OEM Exedy clutch. I've driven around a 1000km after the swap and there has been no change, no "bedding in" or anything like this. Around 200km of this 1000km has been driven on track flat out so it's not like the clutch hasn't had a chance to work.

The Subaru service has taken the tranny apart, balanced the driveline and are just out of their mind about what to do next. They do agree that the situation is not normal however claim that there is no visible issues with the clutch. So they are not going to swap the clutch again for another one for a tryout.

If anyone has finally been able to solve the mystery of the vibrations (without upgrading from stock), then please do let me know. Until then I have to pick routes without speedbumps.

[gpvecchi]

Did they mark the drive shaft position? If not try rotating 90 degrees. Then again, it can be mounted in 4 positions.

[stacyu18]

carrier bearing? or bad u joints will cause that problem also or they may have been dumb asses and dropped the driveshaft and knock of a weight

[johunn]

Originally Posted by gpvecchi

Did they mark the drive shaft position? If not try rotating 90 degrees. Then again, it can be mounted in 4 positions.

If you mean the driveshaft position of connecting to the rear differential, then it didn't make a difference in which position it was. In any of the four positions the vibration and noise were still present.

Originally Posted by stacyu18

carrier bearing? or bad u joints will cause that problem also or they may have been dumb asses and dropped the driveshaft and knock of a weight

Carrier bearing was checked and seemed OK. The u joints would have probably caused issues prior to the clutch swap as well and at higher RPM?

[mattie]

I was wondering if anyone had a diagnosis on this issue, I have also recently changed clutches and experiencing exactly the same issue?

[chaoskaze]

I have the same thing but in 3.5-2.5k rpm .........Maybe it has something to do with that OEM Exedy flywheel not being perfectly balanced?



Just clueless on what can cause it but it's kind driving me nuts.


Someone with any insight? I mean how you know if the so call OEM flywheel from exedy isn't the issue...