I have heard a grinding sound when I am turning in parking lots for the past month or so. When I had the truck up to rotate tires I tried to find some play in the front wheels and couldn't. I assumed that the grinding metal sound (like loose metal fragments being churned in the diff pumkin) was coming from the spider gears or ring and pinion inside the pumpkin. But the other night I had to put it into 4WD and right away there was a vibration. At slow speeds it sounded like "tick tick tick tick" and it got faster with the speed of the truck until it sounded like a vibration. This is at ALL times: going straight, turning left, turning right.

Could this possibly the U-joints instead of the gear teeth? It wasn't grinding, but a consistant rythem.

 

U-joints.

 

++1 on u joints all the way

 

Phew. I was really thinking I needed ring and pinion gears.