Toyota Repair: 1996 Tacoma 4X4, good luck jack, heat shields

Question
My truck has 150,000 mi and has recently developed a rattle that sounds as if its comming from the midsection of the truck. It starts at about 55mph and sounds like a piece of metal that can't get out. I have checked the heat shields and every thing i could get my hands on  on the underside of the truck nothing loose. It's driving me crazy. Other than the noise the truck runs and shifts great. The noise(rattle) is loud to almost gone at times. Universals feel tight. Brakes work well. Doesn't sound like it's comming from the front. Recently replaced exhaust manifold old one cracked-noise seemed to get louder. Muffler and converter look good. Help? Thanks-Dennis

Answer
I may not be able to help you.  
Being there makes all the difference. You could have a drive shaft that has a seperated inner section.  I have seen this from time to time but normally only on the 2 wd models.
You may have to visit the local Toyota dealer to find the cause.
Good luck
Jack