Critical Drew

I'm having trouble nailing down my issue with an intermittent noise and vibration while driving my TT. When this issue occurs there is a strong shake in the car and a "ping" or "clank" noise that seems relative to rolling speed. My initial suspect was CV even though they are new. Both front CVs checked out fine.
with the car on the lift I rock the front wheels forward and back and it sounds like there may be slop in the bevel box there is a brief mechanical slack between turning a wheel and the rear prop shaft turning as well as a noticeable "ping" that seems to come from the prop shaft.??

Additionally: If I hold the propshaft from turning I am able to rotate the right(passenger) side wheel, this also causes the driver's side(left) wheel to counter-rotate. If I let the prop shaft spin freely then turning either wheel doesn't turn the other.

Is there a differential action in the bevel box?
or should the rear output be locked to the right side output?

Any help is appreciated.

Drew

Critical Drew

Is there anyone out there who has experience with these transfer cases?
Can anyone tell me if I should be able to turn the two outputs independently, or if they should be locked together?

Please help guys

tfifeco

Drew,

I have the same exact car as you. the 02 ALMS. I had a similar problem with the ping noise relative to wheel rotation. a week after that happened to mine my clutch and slave cylinder went out, had to replace it. I am assuming you have the 6 speed manual trans? How does your clutch pedal feel? real soft? or Firm?

thanks
Trey

Critical Drew

I do have the 6-speed manual.
My clutch and slave feel fine as well as the shift action in my trans.
My clutch is relatively new it was replaced only about 20K ago.

I did wonder if perhaps The dual-mass flywheel could be contributing, but at this point it still seems to be closer to the driveshafts.

tfifeco

Hmmm, well you could have several things going on, not just one. For starters, did you get your clutch replaced by reputable mechanic? Which clutch did you go with? I went with a racing clutch and Single mass flywheel. I wanted to upgrade to a much better clutch and flywheel.

Have you changed any bushing? Especially the Dogbone bushing at the transmission?

I do know from reading many of these forum posts that a lot of shaking and vibrating can be the result of worn out bushings, again especially the dogbone.

If you havent replaced any bushing then ...this is just a guess but When your clutch was replace it's possible that Removal and replacement of parts could have caused bushings to loosen up even more and gradually cause more and more vibration..... just a thought.

You may want to consult the mechanic that replaced your clutch, i am assuming you didnt do it yourself, regarding the Pinging/clanking noice. it could be related even if your clutch feels fine. When mine made that noice, then stopped, my clutch felt great albeit a bit softer than normal... about a week later when driving ... mashed clutch pedal to the floor and it stayed there. It was actually my hydraulic slave cylinde that went out. I just figured the pinging sound and the clutch were related. Maybe worth getting it checked out

hope this helps

J. Patterson

The Bevel Box runs off the ring gear of the front diff. What you describe sounds normal. If the rear output shaft is held stationary and one front wheel is rotated, the other front wheel is turned in the opposite direction by the spider gears in the front diff. Same thing will happen if the trans is in gear with the clutch engaged. This won't allow the ring gear to turn and the other wheel will rotate backwards. Some have had the carrier bearing on the rear output shaft fail and cause vibration. You might check that.

Critical Drew

Thank you for the input.

I did do the clutch replacement myself because I was putting in a new engine. I went with a stock replacement clutch.

I did not replace the dogbone or the dogbone bushing, so this might be a great place for me to start.

I now have a second bevel box to examine and I see that the behavior of mine is consistent with this "new" box.

There may still be excessive gear noise when rotating the axles by hand with the vehicle up on the lift, but that is hard to determine.

I think I will try a full fluid swap with Redline Mt90 and replacing the dogbone bushing.

Does anyone have recommendations for bushings? stock/ aftermarket? etc

tfifeco

Look up Powerflex polyurethane bushing. Either race or street depending on how firm you want

Critical Drew

I went ahead and ordered the ECS Performance Dog Bone.
I'll report back after installation and inform if my problems are solved or not.

J. Patterson

Good luck! An engine swap is no picnic. I had to replace mine two years ago. (Dropped a valve at a track event--- About it's 40th day on track.)