Has anyone replaced an axle seal on the rear "smart" diff?

[fitzydude]

I'm debating on doing this myself and couldn't find anyone who did it their self by searching. Noticed my rear diff was seeping oil near the passenger side axle input shaft last night, so who knows how long its been leaking. Is it as simple as unbolting the rear axle and sliding out the input shaft or as hard as dropping the rear subframe? I'm a little leery on doing it myself because an Audi mechanic told me audi axle seals are finicky and can continue to leak after you replace them. I also see this is a common problem on 2010/2011 cars.

PS: I've also got an extra bottle of Royal Purple 75-90 laying around, will the smart diff be happy with that? Thank you

[fitzydude]

Well I went to change the fluid tonight and when I took out the fill plug fluid started dribbling out. Meaning the diff was full! Upon closer inspection of what I thought was seeping could be axle grease.

[jran76]

Well I went to change the fluid tonight and when I took out the fill plug fluid started dribbling out. Meaning the diff was full! Upon closer inspection of what I thought was seeping could be axle grease.

Most likely it is from the axel if you don't see a significant amount of fluid (like drops on the ground). My 2012 with 23k miles definitely has some minor seepage from the inner boots closet to the diff, but nothing from the diff itself.

Both the dealer, and shop I go to didn't think it was a big deal now. They did say it's something I'll need to address down the road, but probably not for a while. I also got the impression that removing and replacing the rear axels is not an easy strait forward process. The tech I talked to (who's retired, but trained a lot of the local Audi techs) said it would take him 8 hours or an all day type of job.

[fitzydude]

Thanks for the response. I've been getting the impression it's more difficult than it sounds too. I'm going to have it at Zinks next week to have some work done, I'll have them look it over then. I can't believe your only at 23k!

[ZGskibum]

This:

http://www.audizine.com/forum/showth...wn-Issue/page5

Start reading at p. 5, about 3/4 of the way down, where the link to the TSB is posted. In summary, the problem is a defective seal in the cv axels. Under spirited driving, the oil component of the cv grease separates and dribbles out through the faulty seal. The cv axels will eventually fail, but in more a "long tortuous complaining decline that you're all-too aware of" sort of way than a "sudden catastrophic surprise failure" situation. To fix it, you either replace the axles (parts $$$$ labor $$$) or disassemble then reconstruct the axels with proper seals and new aluminum bolts (parts $ labor $$$$$, plus high probability of breakage during disassembly resulting in need to order parts from Germany). Either way, you have to drop the exhaust and sport diff to get the axels out.

[fitzydude]

Yikes! Well it sounds like I'll be playing the waiting game on this one. I'm still surprised those axles arent easier to remove.

[dgibbs]

I'm getting the rear cv joints re sealed soon on my 2010 B8 S4. As for a lot of things on this car the parts are relatively cheap ($100-130) but it is quite labor intensive, ~5 hours. I too had been told/thought it was the rear diff leaking, but it seems like it is the cv boots. I might as about getting them replaced as well... just in case.