[R1000K3]

I got a new clutch a while ago. It is an ACT clutch and there are no problems with it as far as I know. But since the install I can feel a vibration when going off throttle. It reminds of a rear wheel unbalance since it cannot be felt in the steering wheel at all. The vibration in a no-load situation can both be felt in the chair and in the gear stick, and also be heard like a very low frequency humming.

The wheels are OK of course since they don’t know if the there is engine loaded or not, assuming the wheel bolts are securely fixed, which they are.

The clutch pressure plate and disc are also OK. In case there was a clutch unbalance it would not depend in engine load; it should then also be noted in neutral when reving.

The vibration has no correlation to engine RPM, it is more speed dependent, which indicates the problem is downstream the gearbox (MT). The vibration starts at about 100 mph when lifting the pedal. The car can be accelerated to 280 km/h without vibrations, but starts to vibrate at any speed above 100 mph at zero load or deceleration.

The drive shaft halves are in the stock position.

The most possible cause is something is a bit loose and begins to vibrate when it is not put in tension by engine load.

The car is at the shop right now but in case they have not found the problem until tomorrow it would be great to be able to come with fresh ideas. I gave them a couple of hints when the car was left and they can think by themselves, but any ideas except- buy yourself a Z06, are appreciated.

[tibra1]

PM Mr 5..he has a ton of experience w this clutch

[Mr. 5]

hmm.
The things that come to mind are:

Was the drive shaft put back on correctly?
A wheel weight was knocked off of the rear wheels?

It definitely sounds like a balancing issue though.

[R1000K3]

The rear half drive shaft was not removed and the shop claim they marked and put the halves back the same. I guess a drive shaft unbalance would be persistent and not make it possible to accelerate to 280 km/h without unbalance. The same with a missing wheel weight; it should be noticeable also during acceleration up to high speed, not just during deceleration.

Thanks for your willingness to help, keep it coming

[dzenno]

I was there before with a vibration issue...it turned out it was a bad CV joint on the driver's side rear axle which I eventually snapped at the drag strip...you car is a 6MT so I wouldn't be surprised if it was the same...try pulling the rear axles off and seeing if the CV joints have smooth movement or are binding...

[R1000K3]

Originally Posted by dzenno

I was there before with a vibration issue...it turned out it was a bad CV joint on the driver's side rear axle which I eventually snapped at the drag strip...you car is a 6MT so I wouldn't be surprised if it was the same...try pulling the rear axles off and seeing if the CV joints have smooth movement or are binding...

Thanks !

[R1000K3]

Got the car back from the shop and the problem seems to be fixed. The shop said it may have been caused by the exhaust system was very close to the chassi at some location. So I took a test drive with the mechanic in the passanger seat. It seemed to be OK at some initial tests so I drove further until the oil temp was 80 Deg C and then floored the car on 2nd gear and went WOT up to 6th. The passanger looked a bit shocked so I went off throttle and said I'll take it easy from now. The mechanic said he was surpriced the car didn't slide off road during acceleration. It was for sure a lot more power than he expected in a passanger sedan

I did several deceleration's and the problem seems to be solved. When we was back and I stopped the car the mechanic asked - how far have you been driven? I told him the distance. I mean how fast have you been driving he said. I told him it was until the speedo saturates at 280 and a bit more. He shaked his head when he left the car. They told me to keep the phenomena under observation for a week and come back to tell the outcome. I have to say it is a trusty and qualified shop.

So, I really hope the problem is fixed and I'm 99 percent confident it is.

[dzenno]

Originally Posted by R1000K3

Got the car back from the shop and the problem seems to be fixed. The shop said it may have been caused by the exhaust system was very close to the chassi at some location. So I took a test drive with the mechanic in the passanger seat. It seemed to be OK at some initial tests so I drove further until the oil temp was 80 Deg C and then floored the car on 2nd gear and went WOT up to 6th. The passanger looked a bit shocked so I went off throttle and said I'll take it easy from now. The mechanic said he was surpriced the car didn't slide off road during acceleration. It was for sure a lot more power than he expected in a passanger sedan

I did several deceleration's and the problem seems to be solved. When we was back and I stopped the car the mechanic asked - how far have you been driven? I told him the distance. I mean how fast have you been driving he said. I told him it was until the speedo saturates at 280 and a bit more. He shaked his head when he left the car. They told me to keep the phenomena under observation for a week and come back to tell the outcome. I have to say it is a trusty and qualified shop.

So, I really hope the problem is fixed and I'm 99 percent confident it is.

Great, hopefully that was it...those issues with tranny vibrations can get really nasty to track down..ask me how I know lol

[R1000K3]

Originally Posted by dzenno

Great, hopefully that was it...those issues with tranny vibrations can get really nasty to track down..ask me how I know lol

Yes, I'm not satisfied until the car has proven to run w/o vibrations for some time and during different conditions. But just now it is a great feeling it runs like before