The pcm from an 01 will not work for your 04 truck. The electronics changed in 04.
In pre 04 trucks, the GEM controlled the 4wd shift motor. In the 04+ models I believe it was replaced by a "smart junction box".
The truck in your sig is or is not the one we are talking about?
FYI, most of the time its a shift motor causing issues not the computer.