If you are running LT265-75-16 tires, get rid of that 3.42 rear end or go to smaller diameter tires. You will never have any kind of performance with that rear. I had it on my '92 Chevy Z71 K1500 4X4 with 5.7 engine which had a Jacobs Electronic Ignition and Amsoil dual filter bypass filtration system. The truck by itself ran great until it was hooked up to my 31' Excella 500 then it turned into a different animal. Ran fine on straight road but any hill or mountain I went up was a problem.
'01 2500hd ext. cab, 8.1 litre gas, 5 sp. Allison auto
3.73 rear end
Mag-Hytec rear diff cover
Amsoil Dual by-pass oil filtration system
Amsoil synthetics all around
265 watt AM Solar, Inc. system