Dr. Gonzo

Hi Todd,
this seems to grow into a mystery. So guys, lets brainstorm once more.
Are you sure the noise comes from the rear of the car? This can be misleading. Did you check the front also?
The noise sounds like an oscillation, so it must be related to some springy part (unsprung masses)? I think you checked this alredy, also on the front?
What I would do now: Some workshops are able to check the dampers itself by putting the car with all 4 wheels on a device which simulates the shaking while driving. In Germany you can go to the so called "TÜV" which is the equivalent of your MOT to check this. I believe this would allow finding the culprit.
Cheers

Todd Gibbs

Hey

A mystery indeed! Thanks for the help - talking it through really helps. I will add some info :-

1. Ive rebuilt the entire front suspension and tested/checked multiple times everything is secure.
2. I created my own exhaust (thrilling video on Youtube ). There is nothing rattling there and it is very clear of the car. Wobbled extensively to check
3. The clunk wasnt there in a video I took on 5th April, 2023.
4. No matter how much bouncing/rocking I do in my garage, I cannot recreate it.
5. It really sounds like its coming from that rear corner. I will get my son to sit there and listen with a stethoscope to various areas, including the top of the suspension damper)
6. Its not engine speed/car speed related
7. Any press on the brakes stops it happening. ie Driving over bumpy ground and its clunking, if I lightly press the brakes it stops
8. I've spent hours under the car / in wheel arch looking, testing all bolts/nuts and bushs.Nothing is loose.
9. Its nothing obvious (like battery wobbling or something left in the trunk)
10. Wheel bearings seem fine, as do callipers and pads.
11. I have now resolved the gearbox mounts, its 18mm above the crossmember

Thats all I can think of. I will recored another video with the windows up and get my son in the back to listen/test.

Thanks agian.

CliffH

Afraid I can’t add anything to what you have already checked but just taking a step back hasn’t this…..7. Any press on the brakes stops it happening. ie Driving over bumpy ground and it’s clunking, if I lightly press the brakes it stops…. Got to give the biggest pointer of anything?

Todd Gibbs

Hi Cliff

Absolutely, I hoped the brake pedal was the thing that everyone shouted "its the thingamejig!!". But I think it also can point to a lot of different causes since it changes the forces on many components.

I just got back from a 10min test. It is 100% from that corner.I'll post a new video

Mrmerlin

Remove the wheel and inspect the lower link pin make sure the cone washers are both present use a flash light to verify both are in place

Todd Gibbs

Update: Ok, with my son in the back he confirms that its the damper rattling around. Leaning/reaching back I can just touch the top of it and I can feel it wobbling around and the clunk through it.

Looks like Im taking the suspension apart... Will post back once I locate the offending item. Thanks for the help so far!

User 3124757575

My mechanic said the same last week about my RH rear noise on occasionally bumpy corner turning. We looked and the CV wasn't split on that side (split on the other side though) , however the grease was all crusty / dry and there was some slow seepage which must have caused it. Mine are being rebuilt as we speak.

User 3124757575

Well done.. it did cross my mind. My rear suspension is so crusty that Ive ordered a set of GAZ coil overs built up so that the top setting is OEM height. Getting any sort of parts for the suspension is either stupidly expensive or not available. New top mounts front and rear are a must!

C531XHO

Highly recommended
"Everything at the Back" - rebuilding rear suspension - Rennlist - Porsche Discussion Forums

and note also the issue of shock orientation when you put it back together
Rear Shocks - orientation - Page 2 - Rennlist - Porsche Discussion Forums

Darklands

I think you can order the whole suspension parts from Porsche and Prekom. After that you have a 5.000 € hole in your pocket but the suspension is all new.

http://prekom.si/porsche-parts/porsche-928/

Todd Gibbs

Hi Guys

As promised, an update.

Original clunk video -
https://youtu.be/9OAgaRyZ40s

Disassembly of rear suspension video -
https://youtu.be/-Tful59LmjI

Today I dropped the parts at my sand blaster & powder coater guy. Looking forward to getting them back, reassembled and back in action - let’s hope it solves the clunk.

thanks for all the help - will post back once it’s all rebuild and tested

Todd

Todd Gibbs

Posting back as promised to wrap up this thread for others with similar problems.

The noise was a failed rear damper. I replaced and all good.

Video proving fixed here The 3 previous videos on my channel are the fix.

Thanks again for all the pointers/help guys!

Todd.