Mrbeans

I'm in the middle of of a sas on my 98 2wd runner that I'm converting to 4x4. Question is, is there a transmission control module separate from the Ecu or does the ecu control my transmission. I've already picked up a 98 a340 with transfer case on left side but don't have all the wiring for the 4x4 tranny. And is they a separate transmission harness or is that part of the 5vze engine body harness