[olddog]

I was involved in the installation of a large industrial drive shaft going to a pump (about 10 yr ago). The rpm is bellow 50, but the torque is above 10,000 lb-ft. The company recomended a minimum of a 3 deg angle. If the angle is straight the needles will not turn in the cups, and the grease will not be rolled around the bearings, causing failure. The maximum angle is fuzzy in my mind, but it was a single digit number or slightly above. The maximum load capability was at 3 deg and dropped as the angle increased. The drop off was exponential as the angle increased, as I remember the chart.

I believe these concepts directly applies to autos, as well.