Outer Limits 4x4 Board

Hi people. Hopefully someone can help me.The other night I locked the hubs on my 1990 4runner to get though a bit of mud in low range.I only had to drive for about 20 meters in the sticky stuff and I was on the road again pulled over unlocked the hubs and drove off. I noticed strait away that the front end had a vibration. This has happened before and only after locking the hubs and using 4wd. The next night after work I got home jacked the front end up and turn the wheels by hand with the hubs unlocked and it seems to be coming from the drivers side front. When I lock the hub and turn the wheel its smooth again. This problem has fixed it self in the past but as my misses drives it daily I have never noticed when it has gone away. Also if it helps, when the left hand hub is locked and I turn the wheel the drive shaft spins but if I do the same on the right the drive shaft won't turn. Thanks