Re: 6.1L Transmission
IMO, because Chrysler is stupid. The NAG1, IMO, is far superior to the 545RFE. I have the NAG1 in my Hemi LX and it is a true autostick transmission with better (closer) ratios (except in first gear) than the 545RFE in my Jeep. I will say that the 545RFE, aside from the crappy ratios and the "takes forever" 4th or 5th to 2nd forced (WOT) downshift, can be made to be "tolerable" with a few simple, inexpensive modifications. What I did to mine is a Transgo Shift Kit, a Sonnax Line Pressure Booster and, with the Advanced Transmission Tuning Application (ATT) on the Superchips Tuner, set up my own custom up/down shift schedules and torque management settings. I think, without a performance rebuild, it is now about as good as it can get.
05 LX/RT & 06 WK/GCO, modded similarly, MDS "ON" Light, Vortex Gens, Debadged, DashHawk, BT Catch Can, SRT CAI W/Add Air Inlet, K&N Filter, Sonnax Trans Press Booster, SC Tuner W/Adv Trans Tuning App, DS Tuner, Cust tube headers w/3 in. catback, Bilsteins, SRT frt/rear bumpers, Eibach SRT Lwr Sprgs & Sways, FRI Sidewinder Cam Adv 2*, 6.1 valvetrain, SLP 25% UD Pulley, BBK 90mm TB, SOS Coils/.060 plug gaps. 20 in. SRT Reps.