Ok, replaced both u joints and the 35mph shake is gone. However, there is still a rumble. It's more subtle, it speeds up when I accelerate. I'm thinking drive train/trans? 40 mph ( rur..... Rur..... Rur..... ) 50 mph ( rur.. Rur.. Rur.. Rur.. ) De accelerate ( rrrrrrruuuuuuurrrrrr... )
My first guess would be pinion bearing. Is your pinion seal leaking/wet? How is the fluid level in your rear end? this is all based on your description and my interpretation of the "de-acceleration" noise.
Just topped off the rear differential fluid, I'll check the pinion seal in a little. Edit: It's not leaking in the back, seals good.
that does sound like a bearing in the differential. its pretty easy to pull the front pinion support out of the diff. you just need to take off the drive shaft and then the 5 bolts that hold the support into the housing. have a drain pan under it and it and pull out on the yoke. pay attention to the shims clocking to the bolt holes. it only goes on one way. once you have it out, hold the support and rotate the pinion. it should rotate smoothly with no perceivable rough feel. also see if the pinion can be moved forward and back in the support. it should have no perceivable movement in the support. if all that feels good then most likely the carrier bearings in the differential.
