I have two probelms with my 1999 Duarngo 5.9. One is the motor will not shift from 2nd to 3rd unless I lift the gas for about 3 seconds, after every fluid change it will shift right for about 2 days...Any help? One other problem is the motor will heat up to about 190 and I just put a new thermostat in it. The problem is the heater is not very hot! Any help is apreciated.

 

Have you had a full trans service yet? If not your filter might be plugged, or you or the shop might have put the wrong trasmission fluid in. The trans can only take ATF+3 fluid. If someone put in a different fluid, you should have the system flushed and filter replaced and have the bands tightened. The last thing I would do is replace the sensor on the trans and rear end speed sensor. It also could be your Throttle Position Sensor.