Good morning,

I have a 2003 trailblazer and trying to figure out if i have a transmission issue or not. i have taken my vehicle to two shops and they have found nothing. I was wondering if you could guide me in the right direction with what might be wrong or what i can ask the mechanic to look for.

Problem:
1) Lost about 2-4 mpg
2) When I am going about 50 mph on a slight incline with the throttle being steady:
the rpm's jump up and down until i step on the gas or let off
the car seems to bog down
3) When i have the cruise set or just footing the pedal going 70 mph'ish on an incline
The car bogs way down and then decides to shift down which then revs the engine way up.
This doesn't happen all time and the engine light does not go on. Could this be a transmission issue? electrical? etc.