2.5tdi quattro, thuds from under the car?

[million]

Since recently buying the car I've noticed she thuds from what sounds like central mid to rear portion of the car. This happens mainly while pulling away and can be felt as a few thuds in quick succession and also as strange vibes while trying to accelerate hard through the gears. She also lightly thuds while letting off while on the motorway. Only seems to happen after driving for a few mins and the transmission has had a chance to warn up leading me to believe it could be diff related...and after finding this post (at the bottom) it seems to tick all the right boxes.

Not sure where to go next other than having this all checked out properly but has anyone else experienced this? Can the diffs be rebuilt or is it a case of trying to find another quattro being stripped and broken? And if I'm in there is it possibly to change the bias to add more power to the rear and or retro fit parts from newer (likely lower mileage) models?


Audi quattro thud/thump help!!!!!! (http://www.audizine.com/forum/showthread.php/456453-Audi-quattro-thud-thump-help)!!!!!!

[zollaf]

prop bering, diff bush, something else loose. get under with lever bar, check for loose things.

[million]

Hoping it's something simple like a diff bush but why would that only play up when warm?

While the clutch and flywheel was being replaced last week the prop bearing was said to be good. Hoping to get to Chris in north London sometime this week.

[zollaf]

no ide why its just when its warm, maybe you drive that bit harder when the cars warmed up a bit ? or just because its and audi and it can. :)
let us know what chris finds.

[million]

Yeah I definitely will. There's loads of threads out there with this or a very similar issue and none of them have any conclusion or resolve...save for matey boy in that link with the worn torsen diff. Gotta say his symptoms exactly mirror mine.

Just out of a matter of interest are these diffs rebuildable or what's the deal?

[mikeybutch]

Centre diff on my 04 had been weeping for months so got it checked out and seal had gone and most of the fluid too.Now fixed and seems smoother .

[zollaf]

not long had the gearbox apart on our a4. took the diff out as one lump and put it back in the same, wouldn't fancy rebuilding one, but worth changing the oil for some nice 75 90 fully synthetic stuff. i use mobil 1 myself, in the gearbox and rear diff.

[million]

Anyone have a spare central diff or box should it come to it?

[SWARCUP]

ive got the same issue at the moment and from talking to a few people if the diff is on its way out there is usually a whining noise, im thinking its the rear diff mounting bushes which when warm are softening up the rubber and allowing excess movement, i will start by changing these first. The bushes are not a solid type they are a spider web design. I have read that you can use sikaflex or tiger seal sealants and fill in the voids in the bushes thus reinforcing what is there at the moment and this can cure the thumping noise. You can change the bushes at home with a vice to push the new ones in if you are a home mechanic.

[million]

How hard is it to remove the diff? I assume you have to remove the whole diff to change the bush?

Reckon a solid poly bush might be the way to go. Only 35 quid off eBay too!

[SWARCUP]

no you can change them insitu, there are two, one on each of the mounts. there is a how to on audizine if you have a search

[million]

Just an update. Changed a load of parts, not all related to the thud issue. Parts changed so far:
Front drivers abs.
Fron't lower control arms.
Drivers side engine mount.
Front engine stub mount.
Clutch and dmf.

Play through the rear diff checks out. All bushings seem tight enough now. Only thing we've found is a bit of slop in the props center bearing bush rubber. I hear these can't be replaced on their own and that Audi are asking around a grand for a new one. Can anyone recommend to me a good Audi breakers or something? Also could any other prop from another model or year be compatible?

[spartacus 68]

Just an update. Changed a load of parts, not all related to the thud issue. Parts changed so far:
Front drivers abs.
Fron't lower control arms.
Drivers side engine mount.
Front engine stub mount.
Clutch and dmf.

Play through the rear diff checks out. All bushings seem tight enough now. Only thing we've found is a bit of slop in the props center bearing bush rubber. I hear these can't be replaced on their own and that Audi are asking around a grand for a new one. Can anyone recommend to me a good Audi breakers or something? Also could any other prop from another model or year be compatible?

Centre bush bearing is common problem. Audi main dealers are having a laugh. You can use a BMW part with a little adjustment on locating bolts. Read this on a B4 Audi quattro, lots of pictures, very informative.
Audifans.net: You are using an invalid IP (http://www.audifans.net/ftopict-29318.html)

[million]

That's awesome news! Thanks mate.

Although...Does anyone know how/if the centre bearing can be removed from the prop. The currant one seems bonded on + can the prop be separated etc like bmw ones?