I just bought my buddys 2006 Silverado 4.8 CCSB - HPTuned, LPP Longtubes, 3" Single Dumped W/ Magnaflow, S&B CAI, 4.56's that has 127k on the motor and 10k on the trany and rear build, rear blew @ 75mph taking the sprag with it so he rebuilt the trans and put new gm locker with 4.56's.
My consern is the 1-2 shift (he says it the servos that their weak from the factory) it takes it a second to shift falls off below 3500rpms and runs back to 4800 fastbut if I get out of it and back in it right @ the shift it shifts fine, I bought a vette 1-2 servo and a billet 3-4 and was thinkig about putting my 3k 278mm yank out of my fbody in it but he is giving me a 3200 circle D or midwest not sure which it is. Would this fix it or is it in the tune?

 

Vette servos helped!