Is there a BTDT listed somewhere?

I just replaced the rear transmission seal (because ATF has been dripping onto the Cats for few months and burning)... but I'm not sure if it is installed right.

I removed the aluminum plate with the old seal in it (from the rear of the transmission). The old seal took a bit of effort to knock out, but the new one seemed to go in all too easy. ;-\ I was actually able to press it completely in using only my thumbs. Also, there does not seem to be any thing to limit the position of the seal -- meaning I could have pushed it right out the other side if I had kept pressing with my thumbs. It's in there, but I'm just surprised that it pressed in so easily.

The car is not completely re-assembled yet so I thought I'd ask if others have any experience with this seal.

thanks!

 

This probably won't help, but:
If we're talking about the diveshaft flange seal on the center differential (where center drive shaft CV joint connects), I'm about to do this job on an '01 A8. A leak in this usually drips on the left side cat...and it should be 75w90 gear oil leaking (kinda skunky smelling thick oil).
The Bentley manual says to pry out the old seal from outside with a flat screwdriver, with plate still attached to center differential (installed in car). So it shouldn't have required excessive force. The new seal should have required a little force to put in...I wouldn't think just "thumb tight" and should have seated into a definite stop.
Is it possible that you drove out a seating ring? ...didn't think there was one, but don't know. Did the old seal look exactly like the new one...esp the outer diameter? What model car?

 

Thanks that helps. Here is some info for you to do your seal.

BTW - There was no snap ring or anything. I was just surprise at how easy it was to press in the new one.

Now that I've been through the exercise....I realize it might have been easier to do things in a different order.

One thing to note...the front half of the rear driveshaft is carbon fiber. When it's wiped clean it's actually translucent. There is a label warning the user not to damage it.

It might not be necessary to remove the cat-back exhaust...but in my case I was doing other work so simply started by removing the exhaust. It's possible that you only need to remove the left Cat, which is attached to the rear pipe with a coupler sleeve. As for the seal, the rear of the transmission (which as you pointed out is actually the center diff) has a removable plate (maybe 13 mm thick) that contains the seal. This plate comes off with ease, and has a heavy rubber o-ring to seal it...so putting it back on is easy. With this plate off, you can tap out the old seal and press in a new one.

So if this helps...here are some hints and steps.
Special tools:
#45 Torx socket
#30 Torx socket
6 mm allen socket

1. Remove the left Cat
Loosen the coupler sleeve, push (or hammer) the sleeve forward and further onto the Cat until the sleeve is clear of the rear pipe. Then remove the 4 bolts for the front of the Cat -- In my case, all 4 were rusted solid and needed to be cut.
2. remove the flexible the heat shield covering the area of the rear seal
-- at this point you will see if the Cat-Back exhaust is in the way or not and if you can get the heat shield off...or if the other heat shields are in the way.
-- The exhaust is easy to remove (although kinda heavy). Once both Cat coupler sleeves are loose, jack up the exhaust 1/4" and slip the 4 rubber hangers off with your fingers...and lower it down.
3. Remove the aluminum shield protecting the driveshaft-to-center diff area. Two bolts, Torx 45 socket, an extension and ratchet.
4. Unbolt the driveshaft-to-center diff.
Pull up the parking brake, 6 bolts, 6 mm allen socket... I used a 1/4" drive with 3/8" adapter, 3/8" breaker bar (cuz a ratchet head was too wide and in the way) and a length of pipe for leverage. But be careful not to damage the carbon fiber driveshaft.
-- pull the driveshaft rearward to clear the lip of the flange, and it should be possible to move it to one side...but if not, then completely remove the driveshaft.
5. with the driveshaft out of the way, remove the bolt in the center of the flange, #30 Torx...and slide out the flange (it may need a gentle tap or two)
- mine dripped a little with the flange out...and at the time I did not realize the fluid was not ATF...and since it had been leaking for a while, I probably need to add some gear oil.
6. I was unable to pry the seal out with a screwdriver as it is shown in the bentley manual. But the rear plate of the center diff comes off easily by removing 4 bolts...I think 6 mm allen.
7. with the plate off, hammer out the seal (which took a bit of force...and so IMO it's impossible to pry it out with a screwdriver)...press in new seal, and reassemble.

If you want to get everything out of your way, start by dropping the exhaust, then remove the three heat shields starting from the under the center diff, and working rearward...then remove the driveshaft. I was also doing the rear diff rubber bushing, so I had to take all this stuff off anyway.

And if your Cat is covered with burned gear oil like mine was, a fine brass brush wheel on a hand grinder cleans it off with ease. I tried a steel brush by hand and it did nothing.

 

Thanks for the detailed info. I've found that Bentley often over or under-complicates procedures. I'd always rather hear it from someone who's done the work.
A procedure I always dread the most is exhaust removal...always a bear, because of frozen and/or rotted nuts n bolts. If at all possible, I'm gonna try to do the job with the exhaust in place...probably impossible, but gonna start that way. I've already had the diff heatshield off and checked the fluid level with plenty of room. I let everyone know how that goes.

I just changed my timing belt and all related components, without any timing tools or moving the front bumper/lock carrier, without a problem...plenty of room to work. Bentley and everyone else said it couldn't be done (?)

Thank again for the tips.

P.S. My model has the all steel drive shaft...I believe Audi updated that between our models somewhere.

 

procedure on audipages.com

 

Just so you know...removing the Cat-Back exhaust was the easiest step of the entire procedure. The connection to the Cats are like female-female sleeve/tubes. You need only loosen the bolts on one end of each tube, then jack up the exhaust 1/4" to take up the weight, and slip off 4 rubber hangers with your fingers...and then lower it down, and grab the tail pipe and pull. I was even able to re-install the exhaust by myself by doing the same in reverse...although it's helpful to have another person help balance the heavy exhaust on the jack and help position it.

If you don't take off the exhaust, then loosen both ends of the one sleeve that connects to the left Cat, and push the sleeve (or hammer it) forward so that it slides further onto the Cat. The sleeve will not move rearward because there is a notch in the rear pipe section. The trouble I had was removing the four 8 mm bolts at the forward end of the Cat. I have never seen bolts so rusted...and I really thought they would either come off or break off using a socket and ratchet -- but it was not to be. The top two are hard to reach with a cutting wheel tool, so I used a dremel carbide cutter (which looks like a drill bit) and was able to cut through them both. It wasn't too difficult, but that particular type of cutter produces millions of tiny metal shards, rather than metal dust like a fiber disc. I was picking metal out of my hands and arms for days. For the bottom bolts, I used a large fiber disc and cut each bolt in like 10 seconds. In case you don't have an alternate vehicle, you might start by finding out if you can get those four bolts out.

While I'm typing...I just thought I should ask -- where is the plug to add gear oil to the center diff? And do you have any helpful hints? All along I thought the transaxle assemble was all ATF, and so I topped off the transmission fluid. But it had been leaking out the rear for quite some time, so now I think I really need to add some gear oil.

 

Filler plug is on passenger side of diff, about halfway up (allen head plug). Drain plug (if needed) is on bottom center, next to where diff bolts to trans.
Car needs to be level and fill till it spills out. I connect a clear flexible hose to the gear oil bottle and squeeze...something I got originally to make refilling front diff on a VW Passat easier, which was actually a little easier to reach than our present problem.

 

Just FYI, the D2 center diff/driveshaft flange seal is a chronic leaker in stock form.

Check with your Audi dealer. An updated flange and seal is available. The flange provides a labyrinth, and the new seal is much more robust. I did my '99 twice in 30K miles before retrofitting with the updated parts. Its been dry now for 60K mi.

Hope this helps.

PS:

BTW, I'm looking at an '02 S8, and the flange area is dry at 90K miles, so maybe the updated parts were a running production change?

 

Thanks for that info, hisport.

Had to contact 3 Audi dealers to find one who even had a seal upgraded 'kit' listed to fit my car ( '01 A8 ).
Includes rear plate of center diff required to fit upgraded seal (they said), seal and drive flange...dealer price total $582 plus tax.

Very intriguing, but a bit pricey which is typical of dealer purchase. Would love to find another source (which I always do on other parts), but came up empty on that search.

Such a common problem (need to replace 3rd seal at 100,000 miles on mine), it'd be fair for Audi to cut us a break on the upgrade...yeah, that'll happen.

 

Meant to say: $582 plus tax was parts only...plate,seal & flange.