I just discovered that my 4 wheel drive is not working in my 2002 Chevy Avalanche. I admit that I am nowhere near an expert regarding all things technical with vehicles. What we have done so far. Put it on the rack and engaged 4x4 button. Front drivetrain is rotating, but front wheels are not moving. Mechanic diagnosed bad actuator. Ordered that and discovered that is not the problem. He has now diagnosed it as something in the front drive shaft where it connects. Quoted a $1,500 fix. Any experience with this? Tips or advice would be greatly appreciated. I am new to the board so I really appreciate all the help.