I have a 78 E250 Quadravan with a 460/C6/NP205 combo with a posi rear end.
recently it has started to clunk in the drivetrain when I start from a stop. It only happens if I come to a complete stop, if I continue to roll it does fine. It also does not do it until after running a while, the first start off in the morning is fine.
It is hard to tell where the "clunk" originates from, it does cause the van to shudder slightly when it happens, it is more than just a noise. The fluid levels are fine and the rear end oil is fine with the right posi additive put in it.
Any suggestions on where to start looking for the source of the problem would be greatly appreciated.
thanks
bob

 

I would check out your U-Joints and maybe check your transmission mounts. Just my guess though.