transmition
 

will a transmission from an 81 cj work in my 96 cherokee, the tranny is off a 4.0 wich i also have im my cherokee. i didnt know if there were plugs that are in the new but not the old. or if it would just go in?

Unless it has been swapped the engine isn't a 4.0 it would be a 4.2. And if the tranny is original then it was never used in an XJ. You should find out what transmssion is actually on the CJ. Hell you didn't even mention if it was an auto or manual.

If its an auto in the CJ then its going to be either a TH400 or TF904/999 3 speed auto. As for manuals there are about 5 different gear boxes used. The 4.2 and 4.0 share the same bellhousing bolt pattern.