Hi, I have a low mileage (under 63k) 1994 GT Auto (probably the 2.73 rear end) that will start dropping out of overdrive (and once out of 3rd down to 2nd) after about 15 mins. of driving on the highway, wind isn't an issue. It will continue to do this maybe every 15-20 minutes while driving until I stop the car. Bone stock car, but it only had about 620 miles put on by the prev. owner in the last 10 years. I flushed most of the fluid, replaced the filter, nothing excessive in the pan, replaced the shift solenoid, still happening. Anybody had this issue before?