Thanks for the reply gearhead,

Sorry I should have been clear on the frame it is actually a 53 chevy 3/4 ton. Because of the same reason. I did not have a gmc engine and wanted to run a inline 6 cylinder and the 235 out of a 56 pickup is the one that came with the 53 frame. It did not fit the gmc frame so I went with the 53, plus that frame had been sanded and painted black already which saved me some work at that time. I am sure the problem is in the drive line having two spots that will slide when there should be only one.

I am planning a trip to the local u pull it and see if I can find one with the same number of splines that will fit and take care of this problem, or another solution.

Thanks Steve