I have a very bad vibration in 6th gear which makes the car undrivable in that gear. There is a little vibration in 5th, but it is bearable. It happens at any speed and only under throttle. It goes away when you coast or depress the clutch. This may not have anything to do with the vibration, but the rear kind of feels unstable at highway speeds and cornering.

I have changed drive shafts, new U-joints, the trans has been rebuilt, installed a Spohn torque arm and had the gears in the rear checked and set up again.

The car has not been lowered and I am guessing that it could use a alignment, but I don't think that is the sole problem (but I could be wrong...). I also have not got a good tune for the car as of yet (using FAST), which could also contribute to the problem because of it running a little rough.

I have done a search on this , but did not really find anything. I have been battling this ever since I broke a drive shaft at the track about a year ago. I could really use some help guys.

Thanks

 

Typically a bad vibration in 6th is due to a missing cylinder (burned/off plug wire, for ex). If you said the vibration was speed related, then driveshaft and rear end problems are more possible...

Dave