C5 S6 Diff bearings?

**ronnie court** · 21-01-2016,01:25 PM

I have a 2001 Audi S6 4.2 5speed tiptronic.

I noticed the inside of my o/s/f wheel was getting grubby so i decided to take a look and as suspected, the inner CV boot had split. Whilst checking the inner CV joint for free play i found there was quite alot of movement in the driveshaft. At first i thought it was just the CV joint, but then found that the whole gearbox flange was moving!! the CV joint seems tight to the shaft, and tight to the gearbox flange, but all the movement is coming from what i believe to be the diff bearing. The other side is nice and tight and firm with no free play as you'd expect.

The strange thing is whilst driving there is no symptoms of this at all, no whining, no noises, no clonks, the drive train is seamless, its not even leaking oil from the diff seal. I have only discovered this whilst looking at the CV boot.

here are a couple of videos to show the movement

Any comments and suggestions more than welcome

**Rob69** · 21-01-2016,01:37 PM

Not an expert on these boxes but if you drop the drive shaft off the gearbox drive flange you will likely see a big bolt head holding the splined flange onto the diff splined output shaft. That bolt is probably loose, you need to get it quick before the splines get too worn and the whole lot needs replacing, it might already be too far gone to save though.
Sure there are other gearbox experts who may know better but I'd suggest you sort it quick !!

**ronnie court** · 21-01-2016,01:48 PM

it does look like they are that kind of setup from the diagrams i have found, if it is just that then that will be a blessing!

i will be taking the shaft off to do the CV boot so will have a look, i'd like to get any previous experiences on front diff problems beforehand so i don't have to keep stripping it down.

Thanks for the reply.

**ametlib** · 21-01-2016,07:52 PM

Hi,
I think the diagrams is not the right one. Am not 100 percent sure ( only 99 ) , but I think you'll find a faulty needle bearing in there. Not much of a help though as the Audi dealer won't sell you a new one.

**ronnie court** · 21-01-2016,09:18 PM

Originally Posted by ametlib

Hi,
I think the diagrams is not the right one. Am not 100 percent sure ( only 99 ) , but I think you'll find a faulty needle bearing in there. Not much of a help though as the Audi dealer won't sell you a new one.

not liking the sound of that

i found an old picture from when i had to renew the outer CV boot, so it does show there is a bolt in the centre i can check initially to see if that's still tight

I've had a read up on ElsaWin and it shows if you remove the driveshaft flange and the 12 bolts around the 'final drive cover' you have full access to the diff (and it will just fall out). Is this the not available bearing you mean?

**zollaf** · 21-01-2016,09:20 PM

nice calipers.

brembo 18z by chance ?

**ronnie court** · 21-01-2016,09:27 PM

Originally Posted by zollaf

nice calipers.

brembo 18z by chance ?

yes (that last pic was just before i painted them)

**zollaf** · 21-01-2016,09:29 PM

oooh they are nice ....

**ametlib** · 22-01-2016,08:56 AM

No I'm not talking about the diff bearing. The needle bearing in question is only there to support the drive flange. If you undo the centre screw and pull out the drive flange, you can pull the bearing out with the right puller.
When I say Audi won't sell you this bearing, that doesn't mean you can't buy one. Just that you can't buy one from Audi....
Last time I changed one of those I got the bearing from Germany, but I guess a good bearing supplyer in UK can find one as well ?