I have a 1993 Ranger 4x4. 4.0L. Engage 4x4 low and go forward the wheels will not lock. In reverse it will. So i lifted the truck up. Took hibs out and the guy who had it packed it full of grease because he said he was snstching on it in the mud trying to pull out a 2014 f-150 in the mud. Well i lifted the truck up. On wheel touching is the left rear. Because of limeted jack stands. Lol. When i engage 4x4 low and go forward the front hubs have a light clicking noise. 4x4 high its louder but will not engage. (By the way i did take the hubs off and clean the grease out and put Some spray white lithium grease and a little bit of ATF in it.) 4x4 reverse it will lock in fully on both sides. Visual inspection of the hubs looked good. No striped teeth. The axle shaft has a little slack in it.(not sure how much is acceptable) i think i have given enough info. Can anyone help determine what it may be? Thanks.

 

The axle shaft turning in either direction should lock the Auto Hubs.
So not sure what the problem would be???
The clicking does mean one or both are not locked

The wheel turning without axle pressure unlocks them, but for this you sometime do need to back up 5 to 50 feet.