worf928

How long have they been that way? It doesn't take a lot of dirt and many revolutions to kill the joints.

If the grease is original then I think it highly-likely that it isn't really grease anymore.

1/2 shafts from Mark are ~$250 per side IIRC, not including core charge.

Pull your half shafts. Pull the boots. Clean, thoroughly the joints. Then examine the ball bearings.

The car in the thread I referenced had less than 50k on the odo. However, the ***** in the one joint I examined had noticeable wear marks in a band around them.

All boots were in good shape and original as far as I could tell. Thus my conclusion, somewhat supported by research, that the grease was toast.

928wolf

I have no idea how long they've been that way, left side had a small hole in it, right side had fully detached from the small end with band, though both were still in place. The car wasn't driven very much for about 15 years, I've put about 5000 miles on it. Never looked closely at the boots until now.

Thanks for the knowledge, I'll report back.

pdejong

Quote:
Originally Posted by pdejong View Post
My '90GT used to have it. It was strictly road speed related. I got totally rid of the vibration after balancing my rear brake rotors.

Peter deJong
Charleston SC

'90GT twin turbo
'83 S Auto
Very interesting- what led you to that as the source of vibration?
__________________
Martin


Martin,

This is a long story, but it was a process of elimination. Solved it about 2 years ago. I had the wheels balanced twice. New tires made no difference either. Ended up putting the car on stands and running in 5-th and 4-th gear on the stands. The rear end would shake between 80 and 120 mph. So I took the wheels off. Ran again and it was still shaking. Took the drive shafts out and ran again: problem gone. Inspected and re-greased the CV joints. They seemed OK. But the vibration was still there. Drove me nuts. The last thing left, was the rotors, when I removed them, the vibration was gone. After balancing them, the car runs smooth at all speeds up to 140 mph. Above that, I don't know

Peter dejong
Charleston SC
'90 GT Twin turbo

M. Requin

Peter, thanks very much for this detailed reply. One for the books, for sure.

928NOOBIE

Hi everyone

I'm suffering from high speed vibration as well...pretty much have for years. I have replaced all brake rotors and no change...I'm going one last turn with wheel re-balancing but I don't expect any difference...it's the same vibration for years.

Question to everyone is that if/when the re-balancing doesn't do the job I'm moving to different wheels. I prefer to stick with 17" unless there is some driving need to go to 18.

I'm interested if anyone has any decent wheels they'd part with and won't mind shipping?

Thanks everyone!

Speedtoys

Before new wheels, get a force-load balance done on them, get the data on the measured off-balance force on each wheel.

Greg Brown was supposed to be doing a thread on an involved process he went thru with someone this last winter on a vibration issue...

UKKid35

A really quick and cheap test is to put it on axle stands, remove the rear wheels, and run it through the gears to 80/90 mph

If you have vibration, try removing the drive shafts at the diff

My guess is that it's the CV joints

All the drivetrain lash in my cars is in the CV joints, because they can wear forever, and almost never fail

So that is where the vibration is most likely to emanate (since you've already dealt with the rotors)

I'm too cheap to replace them, but one day I will, and then I'll bemoan putting it off for so long

Schocki

Here is my experience and finally after many years of ownership my car is smooth at any speed. The high speed vibrations on my GTS were caused by out of round rims!
I went to a shop in Bucharest with a Hunter Road Force Balancer and it revealed three bent rims. One rear rim was replaced 4 years ago with a new one from Porsche due to a crack. This one was not the problem.

They offered to repair the rims, but I opted to buy new ones from Porsche. I just don't like to drive on the Autobahn again one day and to think to myself if the guys in the shop have done a good repair job.
Pricey but FMPOV the only way to go. Swapped the RDK sensors into the new rims today and got my 4 year old Michelin Pilot Sport N3's mounted and balanced.

Test drive: no more vibrations at any speed. Car had vibration issues before at exactly 140 km/h, nothing. Took her up to 230 km/h slowly to give the tires a chance to cause vibrations (like they did before), nothing.

Solution: go to a place with a Hunter Road Force Balancer and if they can't get your road force within limits, get the rims checked. If they are out of specification, it's time to get this problem solved.

oups59

I have the same issue. My CV axle are rebuilt units installed in 2002.

I tried to swap wheels (I have 2 sets), replaced the rear rotors, checked ride height....No luck.
I decided to bring my drive shafts to a company that balance/rebuild them to check if they were unbalance.

The result : one was and need a 13g (0.45 ounce) weight !!!

My question : can wear affect that much an axle? Or more likely, it was always unbalanced?

linderpat

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