I've been thinking about swapping a 4l to a 6l in my truck. (2004 GMC Sierra 2500 HD 4x4). Has anyone done this or even know if its possible? Is there a manufacture that makes a wiring harness? Thx for any input.

 

Speartech makes stuff that can do what you're looking at. Might be a bit involved though.

 

How do you do that in the tune?

 

The Speartech harness makes use of an E38 PCM...so...it's natively 6 speed?

 

ok thx ill check them out.

 

I did a little research and I didn't come up with crap unfortunately. I understand it has to be mated to a Gen 4 engine to even work. More electronic bullshit that has complicated the whole freakin universe lol. Damn I miss the old bbc days. Hope you find something though, seems to be a great trans!