More Overheating / odd heating issues

I have a 96 Toyota T100. It’s a great truck, V6 and very reliable with 130+k miles. Here is my questions. I am in the process of moving to New Haven, CT and I am towing a trailer and have a full bed. During the drive the engine started to over heat. The temp gage is more reactive than any gage I have ever seen. It went up rapidly from 2500 to 3000 rpm then dropped just as rapidly from 2500-2000rpm. When I stopped I noticed I had one nearly flat rear tire. After changing that tire I didn’t have any problems for about 900 miles. By the way, I checked all the hoses, around the block and under the truck; no leaks. The overflow tank is fine and the level is about 1/2" over full hot and cold. Then out of the blue it started to overheat again, I stopped checked tires, engine, etc. After cooling I started driving and suddenly the enging was operating exactly the opposite from what it was. Now it is better to drive at higher rpms to keep the engine cool, I can still watch gage movement but it is no longer as obvious. The temperature does tend to rise a bit excessively when idling or running below 2000 rpm. I have a replacement thermostat but I am not able to replace it at this time. Any other tips and advice, explanations why aliens have taken control of my truck?

[b]With the trailer and the load in the box, and if this has an automatic transmission, I’m wondering if the transmission is overheating.

The transmission fluid runs thru a cooler in the radiator. If the tranny gets too hot, it can cause the coolant in the radiator to begin to overheat. Also, you stated that RPM’s jumped up. Well, that’s an indication that the tranny is slipping.

Check the tranny fluid for overheating. If it’s dark and has a burnt odor to it, that’s probably what happened.

Tester[/b]

First I believe tester has the answer.

However your question seems a bit confused. You start talking about over heating and a very reactive temperature gauge then you describe changing RPM which is not a temperature unit.