Don't the rear brakes have the parking brake built in, if thats the case and they are of any kind of modern design they will self adjust when put into reverse and will make a clunk noise.

 

Mine does that quite often too. The mech told me it's the brake pad(s) shifting. Nothing to worry about.

 

Guys! I think i found the problem and its pretty funny. I always heard a loud thump when i backed out of my driveway. I just realized its the doors locking! the seconed you hear it, the redlight goes on on the dash showing the dooks locked!

 

well thats funny, im sure mine is not door locks, as the thump sound happens sometimes, yours is everytime you backup? when you move forward do the locks also engage?

 

Suspension preload?

 

Yes, everytime i back up. If i recall, i think i hear the sound also when i move forward right after backing up. I am assuming its the door lock sound.

 

sorry, again with this issue, dealer really doesnt know what to do, but i still have this annoying problem, anyone that has resolved the problem?

 

I might be off base on the noise you are hearing. On occasion there is a normal clunky type noise from the rear differential when backing up. The "boing" noise when turning the wheel can be subdues by lubrication. My dealer fixed this noise without my asking. I assumes that it was the spring shifting in its perch.

 

is like someone got slammed against the wall next door.

it doesn't happen all the time backing up though. i can't remember when the last time it happened on my car but then again i haven't driven the car much (bad weather)...

 

exactly.you have the same problem, driving me crazy...

 

My C4 does it occasionally, especially after I wash it and it sits a few hours. It feels like the brake, and I assume it is the e-brake "locking" as the water dries and that thin layer of rust forms. It doesn't happen otherwise. Next time I wash the car, I'll back in the driveway and see if it happens going forward too. I suspect it will.

 

Has there been anything further learned about your problem? I have something very similar happening with my 997 gt3 except that my thump comes with a definite suspension shifting (like there's something loose) that you can clearly feel. Only happens when backing and turning at the same time, and only after the car has been sitting for a while.

Rocky

 

no solution yet, I still have the thump, cannot figure out how to replicate, the dealer heard the Thump, they had the car for a week and didnt find anything out of spec, it happens after stopping and turning the car and then braking while backing up. Its not everytime, but it only happens in my office parking, i think it doesnt like the office, the thing is, it sounds like something mayor, anyone figure out whats going on.

 

I recently had mine into the dealer, but they could not find anything wrong. Next week I'm taking it into a Porsche specialist (race shop) to see what they can determine. I agree that the noise and movement does not seem like a minor thing at all and I'm reluctant to push the car very hard until I can figure out what's going on. I really hate not being able to use the car as it was intended you know?

 

i know exactly what you mean, it doesnt feel safe to push the car, i hope they can help you, please post if you get any news, i will keep trying to figure out whats wrong and will post as soon as i have something. thks