Hello I am new to the forum and hopefully posting in the right place. I have a 2002 avalanche 1500 with a 4wd issue. My problem is my front differential seems like it is not engaged when in 4Lo or 4hi. I unplugged the actuator on the front differential and had my friend press the 4hi button as I was spinning the front driveshaft, transfer case seemed to engage and locked the driveshaft. I also noticed that the front actuator would push out when in 4hi or low and retract when in 2wd like it should. I did swap actuator's from my suburban which I know the 4wd works on and still have no 4wd. Absolutely nothing engages in the front diff as far as I know, I can here both actuator's working. Also when I swapped with the suburban it had 4wd with either actuator. I am thinking it is mechanical in the front differential can this be? My dad had the same problem with his suburban and changed the front diff which fixed the problem, which is why I am thinking it is mechanical. What goes bad in these front diffentials that will cause this? Any help would be greatly appreciated. Thanks Matt.