It wouldn't have anything to do with it. You are absolutely right..

Differential, my friend... do yourself a favor: if you plan on repairing this: search around the site (especially in the transaxle forum) for a guy named Terry Haines. He was a DESIGN engineer for the MTX-75 for the CDW-27 platform. I thin his email is:
secondline@ameritech.com (or .net) either way.. search it out.. he is THE MAN to go to. flat rate of $400 plus parts and shipping to him..
Ray