Re: 2002 WJ 45RFE Transmission
Having 5th gear and making the 45RFE a 5-45RFE, is indeed just a matter of programming of the TCM. 5th gear will reduce the rpm during highway driving and increase the mpg. It also reduces the noise.
Is it not easier to let the stealer reprogram your current TCM? If you change the TCM, it will take some time for it to relearn the shifts on your specific transmission, or you must do a quick learn using a DRBIII scanner from the stealer.