Noticed a knock a couple days ago while driving, progressively has gotten worse. Can feel it in the truck when it does it now. Seems to do it at random. Raised the rear end tonight and put it in gear. There is a noticeable grinding noise...with the tire off the drivers side comes to a stop while the pass side keeps spinning. Almost looks like it has a wobble as well. Any idea what's going on? Hoping it's something with the drums, and not something wrong with the axle.