grinding back end

hi did anyone solve this ive got a 2002 a4 avant 1.8T quattro and it thumps on the back end when driving hard 1st and 2nd gears when letting off to change gear and it thumps all the time when going up a steep hill at slow speeds it like somenones got a rubber mallet under the car lol,
ive had a rear diff oil change with gl5 with no difference , also the rear tyres are different treads new on drivers side and half on passenges would this make a difference?
it also makes like a grabbing noise when im turning sharp left or right pulling out of a junction can anyone help as there seems to be a very lot of this type of fault on here but no definate fix , my car has done 163k lol but runs like newish.

hi guys,

I have a very similar problem with my 2.5TDI B6 Quattro. More specifically these are the thump thunk noises it makes and that I don't find normal. They are actually killing me:

- with the car full, or on a steep hill, from stop, accelerating slowly, I will hear a thump.. thuump.. thuump noise until the car picks up speed. this happens with the clutch completly engaged. The noise goes away as soon as the car picks up some speed, like 15-20km/h or so.
- with the wheels at full lock, either right or left. from stop accelerating slowly, the thump will be heard and the noise can actually be "seen" by looking at the front wheels. They seem to "vibrate" I really cant find another word to describe it. The grippier the floor the harder will be the vibration.

I have replaced the controller arms with a full kit from Febi, my mechanic says everything is tight except for a little play on the drive shaft, but he says that shouldn't be the cause of the noise. it is the cause of a similar thump noise that I hear when shifting, but this is a single thump that can be associated with that particular play on the drive shaft.
I have also replaced the oil on the gearbox and rear differential and my tyres have the same wear.

I also tried to drive with the wheels full lock with the hand brake applied, to try to take the rear diff out of the equation, as so as to only have the front wheels driving the car, and the result is the same.

The car does this since I have bought it one year ago and it really is driving me crazy. If anyone can give me an insight on this I would be very grateful.

thanks!

I had the same issue in an automatic rear wheel drive Omega. Took it to every mechanic I could think of and they said no issue with diff mounts, diff was on its way out.... etc. It wasn't until I took it to some old mechanic who grew up with rear wheel drive cars that he managed to find the problem.

He tested it by applying the brake and giving the car some gas. The idea was the car won't go anywhere but any mounts will move when the drivetrain tighten ups when power is applied..... clunk, clunk, which was coming from the diff mounts. The mounts they look fine and solid unless you jack the diff up which will show the diff coming away from the mounts, which I'm 100% sure no mechanic will do because they are looking for splits, cracks, etc.

Not sure the Audi ones are the same, but I would put money on it being mount related in at least most of the cases following my own personal experiences. Just an idea guys before you go spending thousands on diffs.

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Originally Posted by warp_speed

I had the same issue in an automatic rear wheel drive Omega. Took it to every mechanic I could think of and they said no issue with diff mounts, diff was on its way out.... etc. It wasn't until I took it to some old mechanic who grew up with rear wheel drive cars that he managed to find the problem.

He tested it by applying the brake and giving the car some gas. The idea was the car won't go anywhere but any mounts will move when the drivetrain tighten ups when power is applied..... clunk, clunk, which was coming from the diff mounts. The mounts they look fine and solid unless you jack the diff up which will show the diff coming away from the mounts, which I'm 100% sure no mechanic will do because they are looking for splits, cracks, etc.

Not sure the Audi ones are the same, but I would put money on it being mount related in at least most of the cases following my own personal experiences. Just an idea guys before you go spending thousands on diffs.

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I tried something a bit diferent that I forgo to mention. I had the car lifted and brakes applied, first gear on, and them release the clutch. The person inspecting the car bellow didn't find anything and also no thump was heard ( besides the single thump that comes from the drive shaft because of a bit of play ).

anyone sorted this yet? mines still as bad

weren't able to sort it out yet :(

could it not be a broken spring? Just found out at the weekend that my 71k mile A4 needs two rear springs. Supposedly common on A4's, spring ends are broken. Only had a clunk when going over a bump though.

I managed to fix one the "thumps".

When I bought the car it had 235/40-18 tyres ( mounted on ET35 wheels ), two bridgestone potenza 95y re050a on the front and two bridgestone potenza 91y on the back. The car made the noise since the purchase and the tyres had little wear. I moved the front tyres to the back and the back tyres to the front a couple of months ago but the thump as still there.

Last week I replaced all four tyres with Pirelli cinturato P7 245/40-18 ( used, a bit more than half thread still there ) and the thump noise is completly gone. At first I didn't want to belive it, but after one week not a single thump and I did try everything possible to hear them again..