ITSWILLIS

First time posting

I've had a rear end vibration that comes on only at 80kmh/50mph that is accompanied by what I can only describe as low volume thudding sound that goes away after exceeding 90kmh/55mph. I have done all the following to try remedy this issue.
-PPF realignment
-both rear end wheel bearings
-new tires/balance
-new rotors and pads
I am running Polly diff mounts and a 2-way lsd.
I have also lifted the rear end on jack stands and ran the car to 80kmh/50mph while looking underneath and listening with a stethoscope to the diff,hubs ect nothing nothing out of the ordinary. Feeling with my hands the vibration can be felt mainly on the ppf and through the car itself.

any help/tips are appreciated. Thanks
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themonkeyman

Check the runout on your axles, I’ve seen some that are way out. Also maybe double check the driveshaft. are you positive it’s not from the front end? Could also be a badly worn shock

ITSWILLIS

Thanks for reply, I'll check the run out on the axles. And turn the driveshaft 180° and double check the uni joints. Don't think it could be the shocks as they are new bc racing coilovers

themonkeyman

Ah I see. Well, make sure the mounting hardware is all tight, make sure your suspension eccentrics are all tight etc. I’d just do a full nut and bolt check on the whole car if you’ve got a mystery vibration.

mrejda

This solved a mystery vibration I had around 60-70mph. Good luck!