Rear diff leak

[Skull]

What could be? Is there any seal right of the draining bolt? Im new to quattro, and when i took a look what must be done to remove the diff i felt sick.

[Acidburn]

Best thing to do is to give it a clean and find out where its leaking from as its hard to tell from the pictures.

I helped david (s2driveruk) remove his diff and change it for a 20v quattro one (the driveshaft cups need changing if you go that route) as the units generally have less abuse/power thru them. When doing the cups on the passenger side there is a seal which is like a spring that sits inside on his the first time we did this it was not on right so did not seal and leaked out that side so it could possibly be this, if it turns out not to be the plug.

If you check out project 'can of worms' there should be some pictures and info which could help.

[Jon441cc]

I thought the gear ratio between the S2 diff and the 7A diff were differant

Agree with Acidburn on giving it a clean to see exactly where it is coming from

[Acidburn]

David's been using it for a while now and took it to the ring as well and have not heard no loud bangs recently so afaik its all good.

[Jon441cc]

Yes ive been in davids car and i didn't seem to notice anything wrong


Takes around 2 hours to remove the diff if everything is seized on solid you will have to fill replace diff gear oil though, crack the drain then the filler plug before removing

[LHD_Kid]

Agree, give it a good clean to see where the leak is... If it is from the input / output shafts seals rather than the filler or drain plugs you can easily replace the seals without removing the diff itself... the input shaft seal is more difficult though... either way, I am guessing you will need a top up of oil...!
Gooc luck
Chris

[Skull]

Acidburn: this car is an 2.0 16v, so the rear diff should not have been abused. 140hp is nothing i guess.

I will clean it and then see.

[s2driveruk]

no the only difference is the bolt hole spacing on the diff flanges, so you just need to change them over.

Looks like the oil seal has gone, actually not a major issue and can be done if you're not too fazed by some DIY. I did the otherside quite quickly, just need to lever the old seal out. On that side though i cant remember quite what that seal looks like but if i get a mo I'll see if i can get a picture off my old diff in the garage

Yeah, actually there is a little bit of vibration at very high speed on the drivetrain on mine so could just be slightly out of line with the prop but other than that, now dry as a bone and very quiet, stood up to the Ring and Coombe nicely

David

[Jon441cc]

Its alot easier to clean the diff and replace the seals on a bench than doing it upside down with crap flying all over your face

[Acidburn]

Hmmm didn't know you was getting any vibration, think we need to get your prop done then we can check it out.

Its a pita getting the driveshafts out if they ain't been out before just use a mallet to knock them till they pull out, then its an allen head bolt that holds the cups in.

[s2driveruk]

to be fair the vibration is at about 125mph seemed perfectly ok on the rolling road though so nothing major i don't think.

@ JOn yes thats very true, done both and prefer the bench technique lol. Having said that access to the diff through the wheel arch (wheel off naturally) was pretty good. Just need to ensure you have the right spline keys to get the driveshaft bolts off (m6 IIRC) and as Pete says, a 'light' thwack on the flanges to get them off. Also helps to undo the wishbone at the subframe so you can gently pull the d/shaft away from the diff flange...

[LHD_Kid]

prefer the bench technique lol. Having said that access to the diff through the wheel arch (wheel off naturally) was pretty good.

This is true, its the input seal which is alot worse when still on the car...!!!!

[Dpicariello]

I've got this exact same problem on my car, although it's not quite as bad.
It was suggested to me to use some stop leak fluid that can be added with the diff oil. If this doesn't work then I'm gonna get the whole unit out and repair the seals.

I cleaned the casing a few months back which has really helped to detect exactly where the leak is coming from.

[s2driveruk]

I've got this exact same problem on my car, although it's not quite as bad.
It was suggested to me to use some stop leak fluid that can be added with the diff oil. If this doesn't work then I'm gonna get the whole unit out and repair the seals.

I cleaned the casing a few months back which has really helped to detect exactly where the leak is coming from.

Personally i'm not a fan of those additives, i'd just get the seals done sooner rather than later if there is just a weep rather than a lot of fluid escaping. You can always top up until you do manage to change them and it will be fine.

Might also be worth a flush of fluid too, I refilled my new diff with fresh oil and then the seal failed, when i drained it out i was amazed at the colour (black after 40 miles), it was gold when it went in lol. After refilling i drove to the ring and then checked the level, it was still new looking, so a flush looks to be a good idea

[pixsaudisex2]

as for mister no more leak stuff i canny remember but most diffs etc have a breather on them to stop pressure building up inside the diff gearbox etc.. now if you use super stop leak stuff ( which wont work to well ) it will clog the breather up and the pressure will blow oil past all the seals causing more problems than you had before. but to be honest i canny remember if the s2 diffs have a breather but 99.9 percent of diffs do.