New to hp tuners

Basically I wanna know what I can and can't tinker with to get my torque converter to stop shaking but also put a tune in for pulling when need be! 2017 Chevy Silverado 1500 ( yes 1500 to pull stuff with at the moment) plus can't seem to get speed right. Running 35x12.5x20 and I have to type in 32 and 3.42 gears to get it withing 2mph

You can do both of those things all in the same tune.

Just plug in a tire size that gets the speedo the closest to a GPS reading. Should be able to do 33-34in tires then auto scale the transmission shift points to make it real close.