Banging noise on both sides rear suspension

[Basler]

Hi

I have a 2004 M3 coupe with hotchkis swaybars and Ohlins R&T. Something is hitting when I go over bumps. My mechanic has replaced "everything": RTABS, rear strut mounts, all four trailing arm bushings. Now, the noise is worse. New rubber differential cover with bushing, new aluminum subframe bushings as well. It looks like the noise is in part coming from the swaybars hitting the control arms but we can't seem to adjust the endlinks to stop hitting either the control arms or above, the drive shaft. We even raised the ride height in the back. Any ideas? Have spoken to Hotchkis and they're useless. I know this set-up is pretty common but don't seem to be able to find any info. Thanks

[Cubieman]

Sounds like you need to get under the car and really look around at length at any items that are suspect as it could be anything.

Maybe use some type of paint pen that won't dry so you can see witness marks when something contacts something else.

Also, I would do a nut and bolt check on anything that was recently done to the vehicle.

Beyond that, if you are paying a mechanic, they could use a set of chassis "ears" to more easily find the noise, but that could be expensive as it could take some time for the sound to be pinpointed.

Also, if the car is too low your rear springs may be binding over bumps.

[Tbonem3]

Go back to stock sway bar in the rear. A bigger rear bar doesn't help, just causes less grip/more understeer.

[liam821]

You can always pull the rear sway bar and see if the noise goes away; then you'll know if that's the problem or not.

[mpower22]

Are you sure it's not a subframe failure itself? Pull up the spare tire cover and look for any torn sheet metal.