I'll start with a little upfront.. "what I have is..." stuff. I have a '04 Ram 2500 4x4 as a donor... It was wrecked but the drivetrain is still good. I am putting the 5.7 Hemi/transmission and maybe rearend from the 04 into my 99 Ram ( ditching the tired V6 ). The main question is about the ECM. Since I will have to either replace the transmission all together or at a minimum replace the tailshaft, will the ECM from a 4x4 still work in a 4x2? I know I'll need a whole bunch of other stuff but I have the entire truck sitting there so all I have to do is just grab it and swap. Yes I made that sound easy and I know its not that easy but...

Thanks.

 

Swap the whole engine/trans/t-case, make your life easier. There was a thread in the second gen section where a member was doing this swap.... he also took the third gen dash, and put it into his second gen. Makes getting the gauges and such to work easier..... Use the PCM and wiring harnesses from the donor vehicle.

Folks have successfully completed this swap, but, it is by no means a trivial undertaking.