New Performabuilt 4l60e tuning help

I have a stock 2006 Chevrolet Silverado 4x4 that I just installed a Performabuilt heavy hauler 4l60e in. I have regeared the truck from 3.42 to 3.73. Truck isn?t tune to my knowledge. The transmission has a nice firm progressive shift at higher throttle position but around town at low throttle position around 24% my 2-3 up shift is real abrupt and clunks the transfers case and driveshafts. 1-2 bumps a little more than I like and also it seems to shift too early in my opinion. If I drive it in tow haul it runs the rpms up more and shifts better but still a little too firm. My mechanic is going to help me adjust some shift scheduling with his HP Tuner and I was wonder what are some things I could check/adjust to smooth the shifts up at a lower throttle position. Talking to Performabuilt they ask you leave all the pressure settings stock as they have beefed up the internals to increase the mechanical force for shifting and holding the gears. They did mention checking the setting for the pressure pull back during the 2-3 upshift as GM sets this to .3 to help soften the shift but I?m not sure where this setting is found? Any advice would be greatly appreciated.