well i have a 4l65e fully built i recently replaced my stall from a 3400 to a cirlce d 3800 4c i drove it for a couple days after install with no problems i took a 400 mile trip with no problem on my way back problems started.........
1st. temperature raised from 160 to 210
2nd would not shift into 3rd
3rd rpms would reach 6000rpm and still no shift
4th speed will not go over 45mph

what could be the problem?

 

Sounds like a 3/4 clutch problem. Have you checked to make sure the fluid level is good. Get a scanner on it to see what is being commanded.

Chris

 

I will do that I have purchased new solenoids and wiring for it just in case its an electrical problem............the fuel level seems to be at full what parts make the 3/4 to go bad or fail I know its not your stall it works great also i havent retuned it for the stall size went from a 3200--3400 to CircleD 3800 4C triple disc