my truck is not running right after a repair?

[santino1932]

this is a hard problem to explain so i ll give it a try.i did a trans flush a few weeks ago and now the truck is acting different. b4 the flush it ran fine now when im accelerating the rpms seem to go a little to high and when it gets to around 30mph it kind of sticks there. it seems to pick up speed but when it gets to 50mph it does the same thing and i m not sure if its an engine problem or trans problem. it wasnt doing it when it was colder out either now its warming up and the problem just started. i hope im making sense but the problem is hard describe. im gonna drive it again and add to this question later
the truck is a 1998 olds bravada 4.3 automatic transmission 4 wheel drive
it shifts into gear fine goes in reverse just fine also. tune up has been done also but i do need an oil change cause its due for one.