I stumbled accross this vid that demonstrates Ujoint operation
If such posting is inapproatiate please delete
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That was quite interesting! I never realized that before, which is likely why CV joints are preferred over U-joints.
That's a great video. You quickly go from:
"They say it has to but I don't quite get it"
to "DUH!"
"They say it has to but I don't quite get it"
to "DUH!"
The u-joints at either end of a driveshaft or half shaft should not have operating angles differing by more than ½° from each other. A difference in operating angle greater than ½° tries to make the tires speed-up and slow-down during each rotation; the tires don't want to rotate at a constant speed as this video aptly demonstrates. But of course due to the traction of the tires and the inertia of the moving vehicle this can't happen, so the parts bind, bend and deflect. This is all happening at the "output end", i.e. at the stub axles. The result is harmonic vibration AND severe stress upon the u-joints and stub axle bearings.
This is where two problems arise in independent rear suspension applications. (1) Any amount of rear wheel toe shall horizontally misalign the axis of the differential/gearbox output shafts and the stub axles. Any amount of rear wheel camber shall vertically misalign the axis of the differential/gearbox output shafts and the stub axles. Yet for best tire performance the rear wheels must be adjusted for a small amount of both toe and camber. The misalignment on the horizontal and vertical planes combine to change the angle of the u-joints at the stub axles in relation to the angle of the u-joints at the output shafts of the differential/gearbox. (2) As the rear suspension travels up and down the rear wheel camber changes significantly thus increasing the vertical misalignment between the axis of the differential/gearbox output shafts and the stub axles. This is where the stress upon the u-joints and stub axle bearings is most severe, and it is why the Pantera's stub axle (rear wheel) bearings wear as fast as they do.
This is where two problems arise in independent rear suspension applications. (1) Any amount of rear wheel toe shall horizontally misalign the axis of the differential/gearbox output shafts and the stub axles. Any amount of rear wheel camber shall vertically misalign the axis of the differential/gearbox output shafts and the stub axles. Yet for best tire performance the rear wheels must be adjusted for a small amount of both toe and camber. The misalignment on the horizontal and vertical planes combine to change the angle of the u-joints at the stub axles in relation to the angle of the u-joints at the output shafts of the differential/gearbox. (2) As the rear suspension travels up and down the rear wheel camber changes significantly thus increasing the vertical misalignment between the axis of the differential/gearbox output shafts and the stub axles. This is where the stress upon the u-joints and stub axle bearings is most severe, and it is why the Pantera's stub axle (rear wheel) bearings wear as fast as they do.
Nice info add George. I watched the video and didn't take it to the logical concomitant that our alignment settings for toe-in and camber also compromise U-joint alignment. Also, that is a good explanation for bearing wear. Best case I've seen made for CV joints.