Gotcha.

Is the NP261 the oem transfer case for our trucks? I have a 99' Sierra single cab Z71 that I just bought with plans to follow a very similar build to yours.

Who built your tranny?

Sorry, I guess I should start my own thread..

 

Its the selectable 4wd one with 4lo, 4hi, n, and 2wd. The autotrac cases have auto 4wd.

 

It's only stronger because of the lack of electronic BS.

I had a bunch of problems trying to fix my ol' NP263, I did the NP261 swap and have been incredibly happy with it ever since. It really enjoyed the AMSOIL Universal ATF I put in it too, especially for shifting into 4WD first thing in the morning, in -20*C, so that I could drive through the winter snowfall without having to shovel a goddamned thing. It's been buttery smooth every since I swapped over last fall.

I used to change the DEXIII fluid every 3 months, because of degrading shift quality, but the AMSOIL has been flawless in this unit. My only issue is with the fluid leaking through my weakening output shaft seal.

 

Its amazing the amount of faith they put into that little shift collar and even more amazing that it doesn't shatter. It must be made of weapons grade unatanium cryogenically harded cryptonite.

Is the chain for a NP 261/263 for a Duramax/Allison combination any different or stronger than the chain for a 6.0/4L80E combination? Thats pretty impressive its holding up that well. The 07.5+ 3/4 ton and 1 ton transfer cases aren't durable at all on the 6.0/6L90E applications. The chains stretch like a rubber band even on a totally stock truck, with some abuse of course. I've yet to put a chain and sprockets in a Duramax/Allison 07.5+ truck though.

 

the hd one is 1/4 wider