I have an 03 hummer h2 with a 180xxx miles on it.

i installed the tru cool trans cooler on it last week since an o ring went bad on the original lines going into the radiator so i by passed the radiator and installed the cooler.

First few days the truck ran amazing i put about 500 miles on it. Stop and go highway and trailer pulling. Trans was running amazing!

Until yesterday i drove about 3 miles away and on the way while cruising at 45-50 i tried to accelerate to 60 and the trans slipped and then was fine when i parked. When i left again it was fine until i attempted to do the same again and it slipped again. I came to a stop at a light and tried to drive away with lots of slipping off the line.
So i pulled over checked fluid and it was right at the full mark.

Tried to leave put it in reverse and had basically no reverse. The truck rolled back enough to put it in drive and slowly drive away and limp home with lots of slipping.

I checked the trans pump by unhooking a line to seenif i have pressure and it seems fine. (left anice puddle in my driveway)

i am reading online that it could be a sensor in the trans.

I was wondering if anyone could chime in on any reccomendations to check the trans or troubleshoot a sensor that would cause an intermittent slip

i have no other symptoms no hard shifts fluid isnt burnt smelling. please help i dont want to spend money on a nee trans. I am hoping someon can point me in a direction

thanks in advance

As far as i know the trans fluid is vented and cant have air pockets. And yes i checked the fluid