Difference between gmt400 and 800 axles and diffs?

Blackout

Dat Rust Bucket
Dec 18, 2015
121
11
18
West Michigan
My 03 1500 z71 (10 bolt) has the shitty open diff and I noticed it's getting kind of loose, and I need to change the nasty fluid anyways.

I have a 98 10bolt with a 30k g80 sitting in it out of a truck I threw a 14 bolt in and sold. When I drove the truck before the swap the g80 worked flawlessly and was nice and tight . I'm thinking about putting a locker in this truck to help a little more in the snow and off road without having to switch in and out of 4x4 all the time.

That being said, do I need to swap both the diff and the axles over? One or the other? Or is this not even possible and Im stupid for thinking it is?