I have a 1997 4Runner, Limited, 3.4 liter V6.

I noticed a roaring about a week ago and took the vehicle in thinking it was a bad tire. The first place thought it was a wheel bearing and said it wasn't bad enough to tell which one. I became suspicious but drove on (I have a 52 mile round trip commute daily). The roar grew louder and two days later a second mechanic says its no wheel bearing but, instead, a rear drive-shaft.

This makes more sense in the way it feels and sounds and a greasing of the moving parts quieted the roar somewhat but it has returned.

I need to find a re-manufactured or after market REAR driveshaft. Can someone help me out?

What part of the driveshaft is bad? You shouldn't have to replace the entire driftshaft. Have you took a look at your U-joints? Does your truck vibrate under acceleration? Does it match road speed? Engine speed? Try jacking up the truck and rotating the drive shaft to see if you can identify where the noise is coming from.

Wheel bearing are relatively easy to identify. Jack up the truck and jiggle the tire on the top and bottom. If it moves its a bad wheel bearing.

Also grab on to your driveshaft next to the U-joint and wiggle it around. It shouldn't move.

If you are conviced it's your driveshaft there is normally shops in the area that specialize in building them.

P.S. How many miles are on it?