Your auto t-case has a set of clutches for the front output flange. They are located just behind the front output flange in the rear half of the case.
When you are going under 8 to 10 miles an hour, you get 100% power to the front and rear drive shafts. Above 10 miles an hour, you only get approximately 30% front, 100% rear. If your t-case is over 250 degrees plus, you get zero % output to the front and 100% to the rear.


When you manually shift the t-case into 4wd high or low, the chain begins to turn which rotates the pump and the resulting pressure engages the clutch pack transferring the torque to the front output flange. The small radiator that is located below the passenger's floorboard, is very important to cool the fluid. I have seen trucks with the cooler bypassed and soon after the clutches failed. You will also notice a sensor that is located towards the bottom of the t-case. If the t-case overheats, the #4 solenoid in the valve body will vent so that the t/case will not burn up. When this happens, you will have no front output and there is nothing you can do but wait for the case to cool down.

It sounds like you have a set of burned, waisted clutches.

The last time you went 4 wheeling, were you working it pretty hard? Check and make sure that the t-case is full of oil and all wires are in place and connected.

When you have done those checks, get out your wallet and kiss some money good by.

Marlin