GM-GMC: Clanking driveline, rear axles, chevy 1500 truck

Question
I have a 1991 chevy 1500 truck with 350ci and auto trans. When I start from a dead stop, I can hear a sharp clank from the driveline and can feel the body bump. I have to come to a complete stop before this happens. I have had my machanic check the u-joints and rear end and found no problem.I even changed the front driveshaft yoke but did not solve the problem. A driveshaft shop clain to know how to fix it but after a month the noise returned. I suspect they filled the front driveshaft yoke with grease as I had already done. It also stopped it for about a month. I know two other owners of this model and they have the same problem. Help us with this problem please.

Answer
I have a similar, intermittent, noise in my 1984 K-2500.  I do not yet know what is causing it.  I would have the transmission mount and motor mounts checked in your vehicle.  Any looseness (or a broken mount) may cause the problem that you are describing.  Another potential source for this noise would be worn out leaf spring eye bushings in the rear axle.  However, I have replaced all of them in my K-2500 (front and rear axles) and the noise I have still occurs.  Also, be absolutely certain that nothing can hit the driveshaft during normal vehicle operation (the exhaust system often runs near the driveshaft).