Originally Posted by
bigbutstupid
i noticed that when the sp12x comes in brand new, the diff is rather gritty and not smooth at all.. any tips and tricks on how to rebuild it?
I don't believe the factory assembly includes a good break-in procedure. We always rebuild before using.
The biggest thing is to make sure everything is clean and degreased (we use motor spray) prior to assembly, ESPECIALLY the O-ring (inspect to make sure it is not damaged or flattened with age) and the axle flange groove where it sits. Install O-ring with a lint free cloth since the oil on your fingers may be enough to cause slippage.
Just a VERY small amount of silicone diff grease on each ball after cleaning and degreasing. Sand the diff rings with 600 grit paper, clean and degrease, and assemble per instructions. Take care not to get any oil from your fingers on rings or balls.
Break in slowly by tightening the diff nut until the rings JUST begin to drag on the balls. Then alternately hold one wheel and the spur gear while turning the other wheel, perhaps 6 or 8 revolutions each direction. This process seats the balls on the rings. Then tighten the diff nut just a little, no more than a few degrees, and repeat. Eventually (expect to spend 10 or 15 minutes minimum on break-in) the assembly will be tight to the point that you cannot make the spur gear slip and the diff action will be smooth with very little drag.
When done properly, the Corally diff is as good or better than any.