Final drive fluid test?

[John Larson]

QUESTION: Anybody have any way to test to see if the tranny fluid is
already leaking into the final drive? Seems like you would have to remove
some final drive fluid and test it somehow,

Yup.  With the car on a lift (gotta be level, more or less), remove the diff
fill plug.  If more than just a little oil comes out, it's over filled.
Most likely cause of that is ATF dilution.  It is VERY common.  I went to
auto trans school at VW/Audi in 1973, and it was already beginning to be a
problem in the T4s, the 100LS, and soon the T2s.  As the weights of the cars
and the power of the engines grew, it became more common.  I still see it,
and I know of cars that have at least 4 trannies, all because of diff
failures from swapping fluids.  The ATF is under pressure, the diff oil is
not, so it's ALWAYS the diff that lets go.  Tranny failures come mostly from
abuse and overloading, but also from oil cooler failure, allowing water to
enter the trans and destroying the clutches.  HTH, John