Whitesands

With the car in P or N, I can’t really feel anything at idle but as I increase the revs it starts to get stronger, not strong enough to shake the car, at 2,500rpm the vibration turns into a kind of vroom-vroom-vroom and continues as the revs rise, on the road you don’t the vroom-vroom you just feel the vibration.

As I’m stationary I take it I can rule out wheels/tires/axles, I’ve just had the TT out and fitted 3 of Constantine’s Super Bearings and left out the balancer, I did jack up the engine while it was running to see if that made any difference, didn’t seem to but didn’t jack it that much as I wasn’t sure how much the pan would take. The mounts are 5/6 years old, I’m fairly sure the engine is not missing; the vibration doesn’t feel like that.

Anything I can try to pin point it.

Is it ok to undo the flexplate and run the engine to check that’s not the cause?

Any ideas appreciated as I'm fed up.

Thanks.

Mrmerlin

interesting you left out the damper as thats what it supposed to dampen.
I wonder if the driveshaft might be bent?
did you spin it before installing it,?
\ did the transaxle hang on the driveshaft at any point of removal or install? this could have bent it

davek9

Well any vib is not due to the removal of the damper, I left my damper out when we installed the new Super bearings and my car has never been smoother.

The car will run w/o the Flex plate connected but I have never tried it, also I would not jack up any eng by the oil pan, unless I was going to replace the gasket and with the MMs connected it realy should not move much.

Like mrmerlin said did you bent the drive shaft, could be the TC bearing?

928 at last

You did replace the converter carrier bearings........right?

Black Sea RD

Hi Ivan,

You can move the flex plate away from the fly wheel by removing the pinch bolt, undoing the six bolts holding it to the flywheel and then slide the whole flex plate back from the fly wheel onto the drive shaft.

Then run the engine and see/feel what happens.

As far as the TT dampener, our Super Bearings have been engineered to replace the weight of that piece so it doesn't have to be re-used.

How about the front crank dampener? They have been known to fail and cause vibrations.

Disconnecting the TT from the equation would be helpful to pin it down better.

Please let us know what you find out.

Best,

Whitesands

I carefully checked this before install, the transaxle stayed in the car.

I may try this.

No just the TT bearings

Whitesands

Hi Constantine,

I had the crank damper off not so long ago while doing the wp/tb and didn't notice anything wrong with it but will check it out.

Fitting your Super Bearing did get rid of some of the original vibration, I guess I have more than one causing my problems.

Ivan.

jeff spahn

Subscribed as my car has a vibration I can't pin down. Just doesn't feel smooth and it's coming from the driveline somewhere.

Black Sea RD

One more problem area from memory.

There was a thread on here about a year ago about a torque converter going bad and giving vibrations into the drive line.

This was found by an independent shop and I remember being impressed that they were able to diagnose this failure for the 928 owner who was experiencing driveline vibrations.

HTH,

blown 87

Constintine could tell for sure, but I suspect that I have installed as many superbearings as any one other than himself, I can not see how it could be the bearings at all.
You have other issues.

Bill Ball

Ivan:

Any progress to report regarding your vibration?

PHIL928

This may be the obvious one, but maybe you installed a bad motor mount 5/6 years ago? Or maybe it just perished faster than expected. Would jacking up the engine really do anything? You may just be creating a pivot point for the engine to rock on, and if the motor mounts are seized up you probably will still feel the vibration.
Mine was vibrating terribly at 2500rpm before I did my mounts.

supercedar

I also found that my Cat's were up rubbing the floor of car after all my repairs. The usual TT bearings,MM TC bearings were replaced. I adjusted them downward and all is smooth.
Thomas

ROG100

Always change the carrier bearings when doing a TT. They wear quicker than the TT and are cheap.

NC928S4

My symptoms prior to TT, Carrier Bearing and Tranny Mount replacement were identical to yours. My old TT had definite bad bearings and the Vibration Dampener was sliding for and aft with a thunk under hard braking and hard acceleration. I had done MM about a year earlier which helped the vibration a little but the root cause of my vibrations was TT, CB and TM related.

Prior to this repair I also found the CATs rubbing and vibrating on the Heat shields. Once the repairs were done, all vibrations and rubbing went away.

Also related, was that I had a front rim that needed some straightening and balancing. Having that wheel vibrating definitely made other vibrations magnified. Getting the vibrational energy out of the front wheel calmed the whole car down.

Good luck as many vibration problems are counterintuitive to find and fix.