marine928

I recently noticed a vibration/shudder anytime torque is applied while driving. At speed no issue. Once torque is applied through acceleration the shudder returns until a constant speed is maintained. I had the tires (Mich. P.Sprts) rotated and balanced and a front end alignment done yesterday. No issues and vibration/shudder still present.. This is a recent development. The following has been done within the last several years:
M/M, torque tube ( Constantine) tie rods, shocks, muffler hangers.

Put it on the rack this morning to visually check and found the following:
Minimum movement in tires, either vertical or lateral. However, there is about 3/4 inch back and forth movement in the drive shafts. Is this normal? If not can they be rebuilt or must they be replaced. Any comments or questions will be greatly appreciated.

Marine928.

FredR

The half shaft has to float axially

marine928

Thanks Fred, both boots were ripped as well. I recently replaced the brakes and rotors all around ( 8 months ago) and the boots were intact at the time. Any other ideas?

Thanks again. Lon

Adamant1971

Have you checked the rear lower control arm pins? If a nut is loose that can produce vibrations under load.

FredR

Lon,

The four half shaft joints must have no detectable play rotationally speaking- once the boots go and if you live in a wet environment with a lot of cruddy spray the joints can fail rapidly- hopefully you caught it in time.

As Adam says also check the various joints for correct torque.

marine928

Hi Adam, the lower control arm pins appeared to be tight. I did a full suspension refresh in 2016, have driven about 14k since. Everything seemed to be tidy and tight as far as that goes. I do check it out on the rack 2x a year just to tighten things up. It amazing how oil pan/valve cover bolts can loosen up.
Thanks again. Lon

Speedtoys

Same, TT refresh coming this fall for me to fix it. The bearings/dampers have moved.

Constantine

Both half shaft boots being ripped in such a short time frame seems odd and it could be something going on with the joints.

Recently talked with Sean R. about a customer 928 automatic that had our rebuilt TT installed to cure a vibration which, although it helped, didn't completely take care of the vibrations.

Months later Sean R. finds that one of the half shaft joints at a wheel went bad. Half shaft was replaced and understand the vibration problem was cured. Sean R. can elaborate or correct if I misstated anything.

While under the car again it wouldn't hurt to drop the front flex plate cover and visually check that the front flex plate clamp and first TT bearing are okay.

marine928

Hey Speedtoys, the refresh is such a worthwhile project for overall health of the 928. Budget some extra time and $$ for wyait items. Also take a look at your muffler hangers. They are rubber and do deteriorate from heat and weight of exhaust system

marine928

Hi C,
Thanks for the input. I have your TT upgrade and pinch bolt clamps as well.
Great investment for peace of mind. Have detected no movement at all in three years and up until this issue, my car has been rock solid. Kudos to you and everyone else who continues to prove advanced products to make life easier for us lucky enough to drive a 928!

worf928

I’ve seen this exact scenario with one of my clients.

OP, how many miles on this 928?

Speedtoys

Those have all been done, regret not tackling the TT when I had the trans out last fall. Everything, including half shafts is new.

Constantine

Thanks for the compliments!

Hoping you find the source(s) of your vibe issue.

marine928

Ordered the half shaft's this morning from Roger. Will get them in this week and follow up with the results. Thanks to everyone for your input.

marine928

Hi all, just wanted to update everyone on this issue. Received the half shafts from Roger installation was straight forward. Old shafts were worn and probably could have been serviced and reused. The d/s was more worn than the p/s. New Pilot Sports were installed on rear and balanced all around. Alignment redone. Test drive resulted in some perceived improvement but the shudder under acceleration is still present. A couple of observations: 1. When I put transmission in park there is about 2 inch play (roll) when stationary. 2. There is about a 1-2 second delay from park to drive before the transmission engages. No undercarriage leaks and steering components all in good condition. My torque converter was serviced 5 years ago for the dreaded "rivet" rattle. All rivets were drilled out and replaced with proper bolts.

Any new thoughts?
Thanks,
Lon Davis