I'm actaully getting well I'm guessing the same noise, it sounds like the left hub is not locking or unlocking, I took mine off cleaned it and it didn't do it right away but it did start after about 30s of driving, and of course once I slap it back to 2x4 its gone. I don't even hear the hubs unlock when I put it in drive. I use to feel a big clunk but I try to back up about 6ft or so to unlock them then put it into drive. With whats going on now I don't bother cause they never seem make a sound.