Ive read that if you swap out the tcm on a 45rfe, that you can "upgrade" it to a 5 speed and i was just wondering if that still apllied to the 46re. from what I understand its just a heavier duty model but I want to make 10,000% sure before i waste money on a new tcm. 1998 durango.

 

The TCM can't 'create' new gear ratios, which obviously requires gears (metal stuff). I'm curious where and what you read.

 

the 45 has a secondary 2nd gear reserved for downshifting which if you change the shift points on can be changed to be a fifth gear. at least thats how i understand it

 

Just not sure if the 46re has that redundant gear is all. or if the whole thing is a falsehood.

 

No. The 46RE has three speeds, and overdrive. TCC lockup is NOT another gear, nor is there anything extra in the trans. 4 gears and TCC is all you get.

 

Maybe you can swap the tcm and the trans and swap it to the 5 speed. I’m not sure, someone correct me if I’m wrong, but the 45rfe was 4spd and the 545rfe was 5spd right? If that’s the case, then maybe swapping to the 545rfe and swapping tcm’s will get you a 5th gear. But no way jose for the 46re. 4spd only, those were behind 5.9s. 45rfe and 545rfe (assuming I’m correct about those two trans) they were behind 4.7 trucks of different years.

 

so would thw 545 fit on to t9 the 5.9? they hookup to hemi so they should handle the output. just trying to gey every ounce of performance and the bonus mpgs dont hurt.

 

No they’re completely different. Different engine families and output shafts and everything. Better off to build the 46re or get real serious and 5 speed manual swap it with donor parts from a Dakota

 

as stated this will NOT work with the 46re transmission as it doesnt even have a TCM on it.

the 45rfe and 545rfe are mechanically identical, with the difference being the software used to control them.

With 3 planetary gearsets inside they have 6 forward gears. (5 with a kickdown second)

they are as follows (the 545rfe is a double OD transmission)
1st/rev 3:1
2nd 1.67:1
2nd' 1.5:1
3rd 1:1
4th .75:1
5th .67:1

in this case changing the TCM to one which is programmed to use all of the gearset options you can 'gain' an extra OD gear, but that only applies to the early 4.7 equipped trucks.
<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}-->

 

Good information to know. I stand corrected about the 45 and 545. Thanks for the descriptive information