Adirk - I had a similar issue with my Tahoe and it turned out to be 4WD shift actuator. All the buttons operated indicating I was shifting into 4hi yet it fell like only my front's were locking in but no power. Even Auto 4WD seemed better than 4hi. In 4hi your Tahoe should be able to pull a boat and trailer at a 45 on loose rock. Also check the fluid in your front diff.. when I changed mine it was like watching evil T1000 pour out.
The actuator cost around $60 and can be changed out in about 10 minutes with a pair of channel locks without lifting the truck.
The actuator cost around $60 and can be changed out in about 10 minutes with a pair of channel locks without lifting the truck.
