I just recently found out the vacuum for my front axle actuator for the 4x4 wasnt connected properly. I reconnected it and now my front diff will lock like it should when the 4x4 is engaged. Well I switched it back to 2 high and I had a vibration in the front end for about 5 miles and then instantly it was like I hit a very loud speed bump on the highway and it unlocked and smoothed out. It seems as though my front diff wasn't unlocking, but I am not sure if this would cause a vibration. And a vibration in the bearings or gears would be noticable from normal 2 high driving with the actuator disconnected. I can only assume the last owner disconnected the actuator for due to the vibration. I am just looking for a few pointers. Could the actuator cable be sticking and keeping it locked at the front diff? Reman 4l60 with less than 5k. Serviced Tcase at the same time I did the tranny. Did the front and rear axle service around the same time. Thank you for your time.

 

Check out the Tech Article (DIY) Index for an article title that pretty much sums up your situation.