Hotrod is right. I found out the hard way on ald Chevy school bus that I put u-joints and bearings in. I didn't get the shafts phased right and there was a vibration. When I found out what I had done I felt kind dumb. On this bus it was long enough it had three shafts. One off the transmission, one in the middle of the coach, then the last one connected to the rear axle.

I had one just a couple of splines off from the rest.