philpilot

I get a vibration between 2500 - 3000rpms on moderate to hard acceleration. The car has had in the recent past rebuilt torque tube, motor mounts, transmission mounts, and new spark plugs. The car will also vibrate (not as hard) in neutral while accelerating in that rpm range. My Porsche mechanic can’t figure it out. Any suggestions would be appreciated. It’s a 1990 s4.

M. Requin

I spoke with SeanR about this at Frenzy, and he suggested the harmonic damper as another source, I plan to change mine out this winter because of age (>214K) and an attempt to cure a vibration such as you describe.

philpilot

I have 134k on mine. That’s a major job and no guarantee that’s the problem.

Tony

eh..not that big of a job. just add it to the next timing belt/water pump replacement

Bertrand Daoust

What Tony said.

Also, make sure there's no pressure on the flex plate.

philpilot

Forgot to mention new timing belt and checked flex plate myself.

Bertrand Daoust

Looking at the harmonic damper would be a good thing then.

Mrmerlin

for the OP the vibration you describe could be from a damaged TT damper or it could just not have been put back in.. or the driveshaft is bent.

NOTE Greg Brown makes a driveshaft made out of the strongest man made metal these are burgundy colored so they will match your interior if you have Bgundy

Best option is to remove the TT and send it to Constantine and let them install new TT bearings,
this will eliminate the damper as they will put in 3 new stronger TT bearings


Next best option is to get a rebuilt TT from 928 INTL send them your old one.

Last option buy 3 new TT bearings and rebuild it yourself,
you will probably find you also need a damper buy one at half price sale. verify thet the drive shaft spins true before taking it apart.

philpilot

Any good 928 mechanics in the Sarasota/Bradenton Florida area.