I have a 91 explorer with an auto tranny. The question is what tranny and transfer case can I bolt up to the 4.0 that is stronger than the origional. I realize I will have to probly use an adapter plate to match up holes. Where would I have to purchase this also. I had my tranny rebuilt a year and a half ago AGAIN and it is starting to slip and surge. I am ready for an upgrade. I have the rig lifted with 33 12.50s at the moment and am looking to put a set of 38s at a later date. I'm sure the lift and tires are the cause of my tranny headaches but lowering the rig is not an option.