Alright, so here's the deal, this started recently with my 8.8. I lost 4.5 qts of gear oil in two days through the pinion nut, and it has started some hellacious vibrating at 40+ mph. I fixed the leak (the nut was just backing out) but the vibrating is still there. It's only when I'm on the gas and slightly when the truck is slowing itself down. I personally think that it's the joint at the pinion grinding on itself when the axle is pivoting under load (I have a 4" block
). I think that because this started instantly that it could be because I towed a car trailer with about 500lbs. on the tongue and it wore out my springs(stock with AAL, blocks, and shackles). I got some JD trac bars on the way to fix the pivoting and grinding under load at slow speeds, but is there anyone else that has any other opinions? I've read around and it seems like it's either this or the pinion bearing so I'm looking for some advice, thanks!!!