Quote: I have a hunch the reason many people believe in both methods is simple. The driveshaft to pinion measurement is seldom wrong due to the fact that most cars are built right to start with, with the shaft and engine centerline very close to right. Secondly, it takes a fare amount of improper angle to produce real problems with our type of equipment. The torque converter acts as a cushion, the tires act as a cushion. I got my driveshaft education in the 60s , on a piece of equipment that would tear itself apart if you didn't get it close, or right. A single U joint if run at an angle, and run at a steady speed, will produce a faster/slower motion twice per revolution. It is zero difference to very little at low angles, but grows rapidly as the angle gets further from correct. That is why they phase u joints, and why there are such things as constant velocity Ujoints (shame on me, I just couldn't stay out of it!
why? you are absolutely correct in my opinion. but you can see my opinion doesn't mean much
