Chevy K2500

1. It has a 8-lug, 14 bolt rear axle in it. Does anyone know what the gearing might be?

2. The heat has not been working in the truck and I flushed the heater core with water in the reverse direction and I also changed the thermostat in the engine. Still no heat. What is the common sign that the heater core is not working. The blower works great. The heat control is the electronic style and that seems to be working right.

There is NO feed back from the servomotor to the control head. The control "head" simply issues a positioning command and ASSUMES the motor has obeyed. The bar graph on the control "head" display will move, even though the servomotor DOESN'T move.

You may have a control "head" problem, where the "head" shows the bargraph moving and is defective, and not sending the signal to the servomotor. You may have a wiring problem between the contol "head" and the servomotor. You may have a defective servomotor, OR a mechanical problem, where the servo is moving, and the "blend door" is not. Also, the blend door is plastic, and has a rubber flange around it. Sometimes, the rubber lets go of the plastic door, so the door no longer seals, allowing cold air to bypass the heater core.

LOTS of stuff to check, all located in a MISERABLE place to work!

On the heat deal,did you take out the fitting at rear of intake to see if clear?Did you check the flow from heater core at return side going back to the radiator?~brad