Redline MT90 (GL-4) in rear diff?

[Brady Moffatt]

Hi All,

I've heard the stories warning against putting a GL5 oil in the
tranny/center diff of quattros.

However, the opposite happened to me today. My enthusiastic mechanic went
beyond my instructions which were to change the oil in the tranny of my 83
urq to the supplied Redline MT90. He went and also changed the oil in the
rear diff. He used the GL4 rated MT90 in the rear diff too.

A couple of questions about this:

Will the GL4 in the rear diff cause any problems?

I supplied 4 US quarts of MT90, and he gave me back a full one, after having
filled tranny and rear diff. Seems like a lot of stuff to fill for only 3 US
quarts used. The 83 urq owners manual states that the tranny holds 3.8USqts
and the rear diff holds 2.2USqts of the same undetailed hypoid oil. Bentley
has similar but not identical numbers and specifies GL4 hypoid oil for the
tranny, and GL5 for the rear diff. That's 6USqts total. The mechanic used 3.
So my question is how much of the oil is realistically going to stay in the
tranny and rear diff with all drain plugs open? I know the answer's not
3qts!

This is maddening cuz the guy knows Audis, but, sheesh, how much simpler can
a job be than changing tranny oil?

Cheers,
Brady Moffatt
Montreal, Quebec, Canada
83 UrQuattro with 51,000 miles
86 4ksq with 310,000km
86 4ksq parts car
72 Datsun 240Z with 180,000 miles
92 VW Golf with 200,000km FOR SALE
in middle stages of quattrosis accumulatus


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