242 Full Time problem

This is kind of Mod tech, but deals with a stock 242 t'case.

I swapped a 242 into my ZJ. 2hi, 4hi and 4lo work perfect, but 4 Fulltime is giving me problems. If I shift into Fulltime while in Drive, it works fine until I shift into Reverse, and then it acts like it is in Neutral. Same going from Reverse to Drive. The linkage shouldn't be an issue, it shifts fine through all modes.

This t'case came from a running/driving 98 ZJ with 230k on it. I pulled it and threw it in mine without doing anything else to it. I did not drive the donor in Fulltime, so this may be an issue it already had, but if there is a way to remedy it I would like to know. I am going to leave it installed until after the Crawl in July since 4hi and 4lo work fine.

Any ideas?

I'd first try the obvious and adjust the linkage by the book. I've had my 242 do some odd things, but going into neutral when the tranny is in reverse is a new one on me.