4l60e shifting problems

[BOOHER26]

i have a 00 Denali with a 5.7 and a 4l60e the problem im noticing is that when im accellerating hard the tranny runs high in the rpm's and when it does shift its real lazy. then if im crusing on the freeway and go to pass some one instead of downshifting it goes into some sort of no where land and the rpm's kinda comeup but no acceleration if i slightly lift of the go pedal it will shift back to 3rd and accelerate very slow. It always feels like something is slipping or draggin me down. i am runnign 24's and stock gears 3.73 im changing to 4.56's. soon but it did the same thing with the stock wheels on it? any ideas.

[ChevyTech007]

I would have the pan pulled to check for any material