When I come up to a stopsign I get a clunk sound in the drive line and also when I take off from a stop. I have replaced U joints, check mounts, checked differential and even lubricated the splines of trans drive line coupler with Chevrolet"s blue lub. For short periods its is fine and then it starts again. I noticed when I used the blue lub that it stopped for a while so I suspect the problem is in the lub. Is there any special lub other than Chevrolet's that might do the job?