Hello all! I have a '95 Supercharged with the 4T60E, and have a frustrating issue. The car shifts smooth and there is no slipping, but after driving 10-20 minutes it shifts from overdrive to 3rd. When you show down it drops back to the lower gears fine, shifts fine, but will never go beyond 3rd gear. Let it sit a few hours and it'* fine again with all gears for the first 10-20mins, then OD is gone again and back to 3rd.
I changed the fluid and filter, and that did not fix the issue. I've read there are three selenoids behind the side cover that control the shifts, but before I tear into this thing does anyone have suggestions? I know if I take it to a transmission shop they'll just say I need a new transmission, and this does not "feel" like that. There is no slipping and for up to 20 miles it'* perfect.
Any ideas are GREATLY appreciated, thanks!
*** Moved from Performance ~ Kevin ***