Thanks for the kind words John, let's see if we can get him going.
The '08 has a new design t-case, made by Magna Powertrain.
Not many reports of problems with these boxes.
MP bought the old NP/NV operation from GM and Chrysler, I suspect the same engineers designed the new box, so a lot of the electric circuits are probably similar to the old circuits.
The guys are right, the correct way to locate the problem is to read the trouble one(s).
But without the codes, there are 4 places to consider.
These are old design problems; but may apply to the new cases
The connections under the truck, water will screw it up, check for water and clean
The shift motor has a finger assembly on the end of it, to sense where the motor has rotated. The fingers, electrical conductors, can get knocked out of place.
The switch, has small resistors, changing the switch position changes the resistance and the voltage to the control module.
The voltage value is the position signal from the switch.
The switch contacts can get dirty.
And the last is the front axle actuator. When any 4x4 selection is made, the operated actuator locks the passenger side outer and inner axle halves together.
When this is fully operated, a contact closes to signal the control module that the front driveshaft clutch can be engaged.
