I've got a fair amount of backlash in the rear end, is that the most likely culprit for a bad vibe that comes in with speed? 50+ MPH gets worse.

If so, is it a big deal to rebuild the rear end?

Wheel bearings seem fine, u-joints seem fine.

Also, any place around Riverside, CA that would be a good place to take it?

 

Drive shaft out of balance, bent or unbalanced wheels. One of them would be my guess.

 

Start by having the wheels balanced. Look for seperated chords/ humps.

Then that 4 pc. driveshaft

And check your shocks while your at it.

 

i had the same problem it ended up being a bad u-joint and out of balance drive shaft.... those u-joints are a pain in the ass its almost worth it to have some one do it for you

 

Driveshaft vote here too. jack the backend up and inspect the joints there.

 

Thanks for the tips. I started doubting myself after reading that everyone thought it was the driveshaft or U-joints, so I just jacked it up and took a closer look. Since I had recently replaced the center bearing I was concerned that I didn't get the couplings lined up right (don't know how much difference that actually make) but all the alignment marks were good. But now (maybe after driving it more with the vibration) I can see that the rear u-joint is bad. Hopefuully that will be the problem. I'll let you know after I get it replaced.

 

rear u joint might have enough slop to do that

 

Just changed the rear u-joint (only bad one, the front two had been replaced at some point previously), and it runs nice and smooth again!

Thanks for pointing me in the right direction.

BTW, changing this u-joint = pain in the butt. It was an original u-joint, and it did not want to come out!