Did you install bigger tires?, if so, re-gearing the axles is the way to go and cheaper rather than swapping Transmissions. All transmissions that are electronically actuated and hydraulically controlled are dependent to a computer known as the TCM(Transmission control Module). If your Jeep has the SBEC(single board electronic controler), you will need to buy the whole PCM(Powertrain Control Module) which controls both engine and transmission. they are very expensive. next, you might end up looking for a harness that will link up to the trans. from the existing harness you have on the jeep. thats a headache. i'm sure i've barely touched the tip of the iceberg here but all in all, i would recommend re-gearing the axles.