Oh, yea!

Synthetic ATF.

Synthetic grease.

Synthetic differential.

Synthetic engine oil.

You bet!

Have used all for many years - no issues. The logic of using absolutely the finest lubricants in transmissions and differentials is even clearer than in the engine - they are simply better than any other non-syn alternative - but, since the change interval between trans and diffs is so much longer than between engine oil changes, there is no excuse for not putting in the best.

__________________
George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg