2005 300c Nag1 3.90 Gear swap/trans issues

[Moose]

I have a 2005 300c 5.7, replaced rear end from the factory 2.82 to a 3.90 and now have issues. The mopar TCM (EGS53) that was in the car I believe is now smoked.
I used HP tuners to re-set the gear ratio and tire size and now the trans goes into limp mode with dtc p0614 (ecm/tcm incompatible). I have tried over and over again to try to resolve this. I then proceeded to replace the mopar TCM (EGS53) with the factory TCM (EGS52) and now have a 4th gear ratio error and goes into limp mode. The p0614 dtc is now gone but I can't set the gear ratio to 3.90 using HP tuners.
The production date on the car is 11/04 if that is of any use.

[THXDEAR426]

I had a similar problem when I changed out a rear diff from 3.06 to the Hellcat 2.62. HPT couldn't make the change and my Diablosport handheld was old enough to not have that ratio available...without an update, which I didn't want to do.

I swapped in a 3.09 out of a Scat Charger and using my DS Predator, changed the ratio to 3.07 and it worked. HPT tech support was only somewhat helpful and they eventually said that they had to buy some additional equipment before they could fix my problem. Guess they never did as it's been 6 months or so and no word...and we still see this problem.

Maybe look for a used DS Predator U7135 and make the gear change that way. Good luck and I hope you get it worked out.

[HemiX2]

Maybe look for a used DS Predator U7135 and make the gear change that way. Good luck and I hope you get it worked out.

The only other option I know of is to pick up a Mopar Performance TCM for an SRT. I have an 05 LX (build date 07/04), did the same mod to an SRT 3.06 LSD and this is what I opted to do. This TCM also has all the correct TCC settings needed for a performance Hemi. I also picked up about 1 mpg.....now get 28-30 mpg on the highway with my mods.