This is an intermittant problem, sometimes not for weeks but every now and then the whole front end will start shaking and thumping like I have a flat tire. I pull over as I always do to check for a flat but nothing. And whn I take off it's all fine again. There was one new noise last week when it was really cold it started making a grinding noide from the left front tire. I co-worker who has the same problem with his truck said to put it in 4whigh and drive it for awhile and it will go away and it did. something about moister getting in the auto locking hub? Please advise I'd like to get it fixed before it let's me sit but I don't want to spend a ton of money on an intermittent problem.