automatic trans question

is there a difference in the automatic transmissions between the years, between command and select trac, 2wd and 4wd?

my trans needs to be rebuilt soon, so i was thinking about swapping the trans from a 90 into a 91. the 90 is selling it as a whole or as parts...my trans needs to be rebuilt soon. gonna check it out if the transmissions are all the same.

tia

Assuming that your question is limited to the 4.0L engine, all years used the AW4 automatic transmission. There are subtle differences between/among years, however. For example, the overdrive ratio was changed in 1991 when the HO engine was introduced. In terms of mating up with the transfer case, the early AW4s had 21-spline outputs, later ones had 23-spline outputs.