Was your truck ever involved in an accident? Sounds like the tranny problems my old Volvo had, turns out it was in an accident (read: more than five accidents) and the driveshaft and some other things weren't aligned right and putting a lot of pressure where it shouldn't be.
Have you pulled off the wheels and checked to see that the bolts holding a caliper on haven't backed out and now you're grinding trenches in the wheel? That was my issue, new front calipers arrive tommorrow and now I have to track down a new bolt.
Possibly but I've never heard it getting this bad. It literally shakes the whole car. I'm home for spring break and need to go back in two days. I'm seriously considering leaving it here because it worries me that something will break on the 150mi drive back.
My 97 recentl started making a whining noise while in reverse. Tonight it decided to start making the front axle POP loudly and shake the whole axle. Forward works fine and there is no noise. I'm completely lost here, I would assume the ring/pinion would be fxxxed but it's fine when moving...