Does it happen when you turn?
Does it happen when you are on the gas, off the gas (cruising), or both?
Does it happen when you are on the brakes or off the brakes or both?
It could be a lot of things including a driveshaft, u-joint, low brake pads, etc.
No problem, take a look and let us know. In my mind it's gotta be one of those two things. I could be wrong, but check them out first and see if you can visually see anything wrong with them.
It sounds like it could be the unit bearing. They are hard to check for smoothness completely assembled since you would be turning the axle shaft/differential at the same time. Best way is to remove it and check.