identifying marks on differentials?
 

are there any external methods of differentiating between an auto and manual diff?

I believe they have different companion flanges.

But I don't know if they look different from the outside.

The other option is to turn the flange and count out the ratio.

Dave

The manual pinion flange is about 1" thick, the auto is about 5/16" thick. There are no real identifying marks on the outside of the casing, because it is the same.