Re: Trans/Diff Seal

[chan@seattleu.edu (Anthony K.B. Chan)]

I bought my car used about 5 years ago when it had about a 50,000 miles on
it, by the way it's a 85 5000s with automatic transmission. I get the finaldrive
/differential fluid unit check at every oil change i.e. every 3,000 miles.  
According to the Audi owner's manual it's never need to be check and 
never need to be topped up or change. Anyway I've been taking it to both the
dealer in Seattle for service as well as a small VW/Audi shop for service. 
I always had the oil change at this little shop since it's a little closer,
They always use either Mann, Mahle or OEM filter. But the most important 
thing is they know about the finaldrive/differential fluid problem 3 years
before Audi did any recall about it. They check and top it up everytime.
So far my finaldrive/diff seal is fine, it has just over 122,000 miles on
it. 

The seal was checked by my mechanic when he replaced the some worn out
rubber seals of second gear pistons in the transmission unit. The seal in
questions is metal, if you have seen the two unit separated you'll see
a big shaft sticking out from the back of the finaldrive/diff unit that
goes into the transmission in the back. This is the shaft that the seal in
question is riding on. If this seal went bad then the fluid between the two
unit may eventually mixed together. The shaft will develop some play and 
you will start to hear some grinding noise when you put it in drive. 
My is in excellent shape, absolutely no play! :) Thanks to him! :) he 
also show me a failed unit. He said it's cheaper to replace it with a used
unit than repairing it but then he said they are very hard to come by.
He saved a good used one for himself just in case. 

He told me the reason they failed were because of low fluid level, since 
the unit only hold just a little over a quart when it is full and at this
point the main shaft and seal is only halfway submerged in the fluid so 
just imagine when it is halfway full. Just imagine how hot the shaft and 
seal and bearing get and eventually the seal failed. He said almost all
Audi's auto box leak a bit and if you don't take care of it then it will
eventually run dry, Audi said the old fluid evaporate. I guess topping
up is probably enough if it was done religiously, both my mechanics, he's 
the owner and his mechanic also drive 5000s, 85 & 86 models, one with
90,000 and the other with 170,000 miles on it which are still on the same 
finaldrive/diff unit. They were bought from their customers whose cars
been maintained by them since the original warranty ran out. 

Anyway enough on the finaldrive/diff seals. I think Audi should paid for
the replacement for failed units since the owners were told no care is needed 
for it. Interestingly I remember somewhere in the Hanes manual in which it
mentioned about checking and topping up the finaldrive/diff unit fluid. Maybe
the Brits know something nobody knows. :)

Anthony Chan
Seattle University
Information Services
Adminstrative System

chan@seattleu.edu