4wd problem
 

Hey all, I am a newby here.
I hope this post is in the correct section. My son has a 2000 gmc z-71 1/2 ton P/U. He recently had the transmission replaced due to it locking up on the hwy. (BAD). Since the repair, the 4wd indicator lite does not illuminate, and the front wheels will NOT engage when the transfer case shifter is moved into any of the 4wd selections. When put into 4LOW, it DOES cause the vehicle to operate in a lower gear ratio. When the transfer case is put in NEUTRAL, the vehicle will not move...the motor just revs. I really think the transfer case is okay but somehow (electrical activated front hubs????) the front wheels are NOT locking up.
Due to the fact that my son had just purchased this truck a week or so before it blew the tranny, we are not 100% sure the 4wd was completely functional. However, we DO know the 4WD indicator DID light up then (it does NOT lite up now). The mechanics who replaced the tranny did check out the transfer case when they did the work...and test drove the truck, but in their defense, it's seems like it's working (4wd shifter responds with a clunk, gears down in 4low, and freewheels in neutral)....until you get stuck in mud...then you can tell it's NOT working......
And...the repair shop is 200, miles away...kinda hard to just swing by and let 'em "look at it."
Sorry for the long novel here, any ideas? Thanks a million in advance, Lee

Start checking at the easy end, on the front axle there is an electric actuator and a switch that closes when the front axle is engaged sending power to the indicator light. Check the connections and if need be check for power when the 4wd is selected. The switch part sounds like it is ok but you are either not sending power to the actuator or it is not working. Also check the connection at the transfer case and make sure they reconnected it when the pulled the tranny.

i was going to say the exact same. check all connections.