I have a friend with a 99 GMC 1/2 ton 4wd nbs. The truck has the auto transfercase. The 4wd has always worked in the past, but recently it quit. I checked the front end and the acuator on the front axle. Everything on the front end is working correctly. The transfercase will shift into low, and the motor on the transfercase makes noise when you put it into high range, but it doesn't engage the front driveshaft. Does anyone have any ideas? Any help is appreciated. Thanks.

 

encoder motor needs to be replaced is my bet, if it is the transfercase you can pick them up pretty cheap though

 

Yeah, encoder motor...if he needs a TC I have 2. One reman with low miles and reman with no miles.