A few good updates...
After I picked up my truck from the driveshaft balancing shop, it was 90% better. On the highway, it you really listen, you can still hear a faint noise at the same conditions, but balancing the driveshaft has taken most of the noise and all of the vibration away. If you're not listening for it, you won't hear anything.

As far as the truck's past, I have no history for it. I picked it up from some no name crap dealership in Massachusetts, who said it was a trade in and had no info on it. From what it looks like, it may have been hit before, I see an aftermarket rear door and body work done... The truck's carfax report shows past registrations in Boston, and if you've driven there, you'd know that the roads are terrible. It definitely wasn't offroaded or screwed around with, way too nice of a shape...interior is spotless, less than normal wear on most else...

But what can I say? When you see a great truck, you give it a thorough inspection yourself (and from toyota too), offer a fair price, buy it, and take care of it. Most people (excluding readers of this site) don't understand the 'take care of it' part, but my truck's in good hands now. <img src="/forums/images/graemlins/cheers.gif" alt="" />
Next step: exhaust leak and new shocks...
Thanks for all input, I'm still checking everything suggested out

Ah-- sounds like maybe you fixed the cause of the diff failing anyway. I had my left rear wheel seperate from the truck several years ago--rebuilt the rear, had noise about 3 months later; come to find out my D/L was bent. Wallowed that mo-fo out.

That's a little piece of advice I tend to forget if someone gets a rig and doesn't have a wheeling history for it....

My balance cost me $250 after I R&R'd the ujoints first; how much was yours? Yeaaahhh--they get us up here. <img src="/forums/images/graemlins/evil.gif" alt="" /> <img src="/forums/images/graemlins/evil.gif" alt="" />

This shop was pretty fair up here (RI). $137 including tax for a two piece, and about $100 for one piece driveshaft. Pretty good deal, I'm very happy with it. I can't believe what a difference the balancing made.

I'd recommend to anyone with vibration problems to do this first, although my truck required multiple solutions.