Look at the RPO code. It's in the glovebox. The RPO code for the trans will start with an M. Just have to make sure it's also for a 4x4. Mine said M30 and when you look it up it says "TRANSMISSION, AUTO 4 SPD, HMD, 4L60E, ELECTRONIC". Not sure if it will say different codes if the trans varies, but the RPO codes will tell you everything mechanically you will need to know about it. It will probably be best to just call and ask someone at a transmission shop about what years will work. If they don't know right off hand they should be able to look it up for you.