Moving to CO in two years and as a project i wanna convert to my 01 2500HD to 4x4. I searched and could not find anything on here. I know it would be easier to just buy a 4x4 but I like working on stuff and am a good mechanic in my opinion. Plus I dont wanna buy all the mods for a different engine because if i buy a 4x4 it wont be an LB7. I have built jeeps but those are simple mechanical 4x4 systems. I am wondering what the differences b/w the 2 and 4 wheel drive systems are. Is there a different computer. I know a lot of vehicles have universal wiring harnesses and just dont use parts. Is it the same with the 4x4 switch in the 2500HD's. Also is the allison the same in the 4x4 and 2x4 trucks? Thanks fellas for the advice