Heating Problem

Hello,
I have a 93 pickup and when I switch pushed over to the heat side of the hot or cold air selector, my truck heats up almost to the red line on the temperature gauge before the thermostat opens up. But when it is on the cool side it only heats up maybe a 1/4 of the way on the temp gauge. Is this something to do with the thermostate? I have had some overheating problems in the past and I've replaced the thermostate and drained and refilled the radiator with fresh fluid. Any thoughts would be apreciated. Thanks

I recall something like that with 22R/RE's, except I think the overshoot occurred regardless of heat control position.

The answer was a 2 stage t-stat from Toyota.