Stange Noise!

1995 S-10 Blazer 4WD.

Over the last couple of months I have noticed an intermittent noise that seems to be coming from the middle or rear of my truck. Sometime it is more pronounced that others. The intensity of the sound is a factor of acceleration. The more I get on the throttle, the more noise it makes. Once moving along at highway speeds, the noise is gone. The best way I can describe the sound it a chattering type noise of metal on metal. I have taken the back brake drums off to inspect the brakes on both sides and all looks fine there. I also put the rear on jackstands and turned the rear wheels to see if I could duplicate the sound with no luck. U-joints seem ok as there is no noticable amount of play in them nor is there and lossness in the drivetrain when I get on and off the gas pedal. This noise has me stumped. If anyone has any suggestions, I would sure appreciate some guidance.

Thanks,
Greg

heat sheilds, skid plates and oose mounting hardware. i currently have a 99 zr2 and had the same problem and it was a sheild the the bolt had broken. it was still in it but broken. so get under it and start moving and wiggling the edges of things. nothing should move and if it does, check it