Originally Posted by
trailranger
Well I'm right and I'll stick to it. Take a pizza cutter wheel and cut some slices. The wheel didn't slip yet the contact pressure between the wheel edge and the pizza was great enough to indent and slice the pizza. Since the pizza is being moved by the slicing wheel it can be assumed that wear will happen to the slicing wheel. Yes this is an example of extremely hard and soft materials, but to some degree the softer diff-ring will yield to the harder diff balls at every pass and create wear. The same approch to pizza slicers is how the Chunnel and many other tunnels were bored through hard rock. This is why a diff with minimal slipping will still create a indentation where the balls were running. As long as there are one or two off sized balls, the contact pressure will increase for those balls and increase the wear to the diff ring.
The harder your diff balls and tighter the grade tollerance the less worry about wear. Some racers like me, just run the diff rings for months and months since the secret I found in a smooth diff is, high quality balls, good thrust bearing and cone washers.
Taking the first part first...
There is no wear between the ball and the ring as there is no differential movement. The indents in the ring are caused by the pressure of the ball on the ring, and the very high level of point contact. The indents aren't wear, they are the deformation of the ring under the high contact loads. They look like wear, but they are deformation. It is made worse when dust and grit gets in and gets between the ball and the ring, causing indents (more deformation) in the ring.
Yes, harder diff balls and tighter tolerances make for less worry about the diff being poor, but that's because a harder ball makes a finer track, and the equality of size reduces the pressure needed to make the diff work and so reduces the deformation. And yes, the very last thing you should ever do is have a diff that slips for one nano-second, as that is wear, and that is the fastest route to a scratchy diff! Oh, and not smacking the rear wheels on the boards helps a lot too!!! HTH
