I see now there is a theramostat AP3134945 that I did not replace yet. This is a black plastic flat base that goes under the cycling thermostat. Would this be a possible reason??? or should I be looking at the temperature switch?

OK, I replaced this heater but problem persist. Dryer runs hot for about 10 minutes then shuts off for several minutes then restarts. Smells hot. Doesn't matter if I use auto or timer control or what temp selection.
My dryer does not have a control board.
Could the temp selection switch be responsibile? I have replaced all thermostats, the heater switch (below the fan housing thermostat), cut off switches. Could one of the thermostats I replaced still be defective?
Also, I seem to be getting plenty of air flow out the exhaust pipe but don't have any way to quantify it.
I have invested so much into parts and shipping now I hate to give up but am wondering when to fold.

Great, thanks for the suggestions. It may be possible that I didn't get the drum seal back on right when I replaced the motor. The drum does make some banging noise when I first start it up but then evens out. I will also check the heater as suggested.

Dana

There is a thermal protection thermostat built into the motor, it sounds like this is what is tripping.
This will shut the unit off but you should have to restart it by pushing the start switch..

Unfortunately I cannot find a wiring diagram for this unit, hopefully someone else will jump in with some help. The below is just general info.

Here is a good site with some dryer repair help.
http://www.applianceaid.com/whirlpool-dryers.html

The way most units work is that when you push the start switch power is applied to the start and run windings in the motor. The motor has 2 centrifugal switches which close once the motor is close to operating speed.
One of the switches, switches in the heating coil. This ensures that the heater only runs when there is air flowing.
The other switch, switches out the start winding so that you run on only the run winding.

Note that if the start winding is not switched off the motor will overheat and trip it's internal thermal protect.

I am not sure what would happen if the start winding and run winding wires were reversed. The motor would start but I am unsure if the start winding could keep the motor running on it's own.

Another possibility might be excessive drag on the motor causing it to overheat. Try rotating the drum by hand in the correct direction, it should rotate fairly easily.

When the dryer stops it will re-start by itself within a few minutes. It seems as if it has shut down the motor instead of the heating element. I would imagine that in normal operation the cycling thermostat would turn the heating element on and off as needed. But this seems to be shutting down the motor instead. The cycle becomes shorter as the clothes become dryer which to me would seem consistant with the cycling of the heating coils. When I first start the dryer with wet clothes it will run for 10-15 min. just fine before this starts happening. This indicates to me the start and run wiring would be correct.
There is a wiring diagram on the back of the dryer but I don't know how to read it in relation to the switch wiring on the motor.