transmission shifting too hard

[BMF]

Hi, I have an 03 6 liter and purchased a tuner from Doug, Any tune that I run in the truck causes the shifting to get harder and harder until it now rattles the truck when it shifts, I try letting off the pedal a little and it does not help, this is under normal acceleration. What causes this, is it the tune or the tuner? It runs fine with the stock tune in it.

[PSDPlayer]

So you load a tune in and it shifts ok. Then the next day it shifts harder. The day after that it shifts harder than the day before. How long does it take to shift harder and harder.

[sredish]

that's what mine does a lot of times..... but mine varies A LOT... like it's constantly in the learning stage. One day it'll work great, then it'll just slam from 3rd into second then back into 3rd like it's having power on it for the first time.... the 2-3 shift is the most problematic, inconsistent shift.

Do you have an aftmkt trans or stock?