95 4 Runner Transmission Overheating

My 1995 4-Runner transmission overheats. I had it rebuilt and had the radiator replaced because of a service bulletin put out by Toyota. After the rebuild nothing changed. I have taken it back over and over and they tell me nothing is wrong with the transmission, but it overheats anytime I try to drive it more than 30 miles at any sustained speed. Is my transmission guy crazy or is there another potential problem?

What speed do you drive when it overheats?

If I drive it above 55 for more than 30 miles non-stop, it over heats. I can drive around town all day and nothing, but as soon as I go for any distance at more than 55 mph, the A/T Oil temp light comes on.

Is your torque converter locking up above 50 mph?