What Causes Hard shifts?

I had my tranny rebuilt about 8 months ago and 90% of the time I baby it. All that is done to it is a old edge programmer and a AIS intake.

Sometime's I like to get on it, but when I do, it shifts hard. I'm pretty sure a stock set-up can handle more HP than what I'm pushing.

Any input or advice? I haven't had time to take it back to my mechanic cause of the long drive and it only happens when I'm in the pedal.
He said that the old edge evolution tuners will and can cause this due to sending the wrong info. to the computer or something like that.

Thanks

Did he do a stock rebuild? Ask him if he changed anything with the valve body.

the older plug and plays are known to take out trannys!

I believe it was a stock rebuild and should I go ahead and switch it back to the stock setting?
Should I take it back and have him check it over, it's only done it like 2-3 times cause I just don't get in the gas that hard.

go back to stock and see if it still does it if not you know the prob..... unless its already done damage.... what color is the tranny fluid

I know on my f350/95 had hard shifts. It was the Barometric Pressure Sensor or BPS (i think most do). It had gone bad and if falls back to a defalt setting, so as you wont hurt the tranny. Shifts hard in 1st and 2nd but on highway was fine.It is made to ajust altitude,humitity and shift timing on the trans i think i read it even afects injection timing.... Dont know what yr your truck is but mine was under the dash just beside the steering collum