Why is my rear right tire rattling.

run over something that's lodged in the tire? would spot a severed bolt or cracked suspension frame...anyways the handling would have gone to hell, so take it to a tire shop...and they'll pull the wrench out of the tread for ya~

I checked the tires to make sure there weren't any screws or nails in it.

Possibly sway bar links needing repaired. These tend to rattle and or sound like change rattling in your pocket(if rubber bushing are completely shot).

14 years of reliable service, Dandy is right WORN bushings...by now...have an inspection done by a professional shop~

Is it bad to drive around with them worn.?

Not to bad but not to good either. That being said I would have to advise you to have them inspected. If it is the links they are normally fairly cheap and easy to replace.

That was the 1st thing I checked and they were tight.

Good call Tom.

have seen many U-Joints causing the driveshaft to end up in the road....a couple of times....with the 4wd...there are a lot of moving parts down there...see if that is the funky way in which the sound is happening~

do not drive with them worn...get them fixed~