has a 275/45-20

 

If you are wanting to go through the traps in 2nd, this advice is key. If not you are launching starting in 2nd gear until your TPS reads over 87.5% on the GMT800 4l60e/65e trucks.
Probably not much of a difference as most people do a WOT stomp of the pedal, but if you try and walk it out at les than 87.5% the trans will be in 2nd.

peace
Hog

 

Oops, thats over 81% TPS on the 05-07, not 87.5%.
And it appears that the WOT upshift occurs 2-3 mph higher when the shifter is in D or OD than when the shifter is left in 2nd..

peace
Hog

 

little update on this, had my buddy look the tune over last night, its almost perfect, its 11.78:1 at WOT, the long term fuel trims are 0-2%, no torque management, only thing he fixed was the speedo, he has the unlimited tuning on 99 model years on his HPtuners, so it cost me $20.

it did have timing retard at higher RPMs under a load, 8-10 degrees on 87 octane, i put 91 octane in it, runs alot better and pulls harder in the upper RPMs.