So far, what I can gather is the 86-89 nonADD diffs had a sleeve in the diff that the stub rides on. The 90-95 ADD diff has needle bearings. No idea if the 90-95 nonADD diffs have needle bearings or sleeves. I've heard people say that if you swap the nonADD shaft into an ADD diff, that you need to remove the needle bearings and press in a sleeve. I mic'd the ends of each shaft and they were identical, so I lift the needle bearings in. Haven't had a chance to really test it out other than 2 minutes in a field, but I doubt it will hurt anything. If it does, I'll be sure to post it

Also, adding the nonADD shaft to an ADD diff requires installing a seal where the shaft slides into the diff