A few weeks ago when shifting out of 4 wheel high, it wasn't wanting to disengage. I re-engaged, and there a a loud clunk by the left tire, but after that 4WD disengaged and everything worked perfectly fine. I have an older Toyota that clunks all the time so I didn't really think twice about it. Two days ago we got a fresh foot of snow and where I was parked I had to shift into 4WD to get out, high wasn't working so I shifted into low. I crawled out of the parking spot, and went down the road a bit to turn around. As soon as I turned left, the front drivers side tire started to bind and I couldn't go forward anymore without feeling like I was going to break something. I also smelled something burning. I reversed and it was okay but as soon as I tried to make any left hand turn it started doing the same thing, minus the smell. I figured it hadn't disengaged properly, I put it back into 4 high and it worked perfectly. I figured it was fixed! I went home and my road is very steep and requires 4 wheel low. I made it up the road fine and went to turn left into my driveway and the same problem reared it's ugly head again. My husband thinks its a bad hub assembly/wheel bearing. I do have a humming noise when I drive but attributed it to road noise and loud tires. Any help or ideas would be greatly appreciated! Thank you!