Poor Little Cone Style

Someone sent me a link to this thread and asked that I give my 2 cents. First, I agree that if done correctly, the cone type sure grip units can be rebuilt to be as good as or better than new. However, I would say that 20%-30% of the units are damaged beyond repair because a spider gear seized to the cross shaft causing the shaft to spin in the case.

The method discussed here about machining .100 off the bottom of the cone and installing a .100 shim to compensate for the material machined off the cone is not the correct way to do this. The amount you machine off the cone has no connection to the thickness of the shim needed. Think about it, after you take about .005 off the bottom of the cone, it will no longer be bottomed out in the case. After that, it doesn’t matter if you machine .030 or a half inch off the bottom of the cone, the distance that it sits in the case will not change. The correct way to select the shim needed, is to assemble half the unit and put the cross shaft and spider gears into position. You want to select a shim thickness that will allow just a very little bit of backlash between the spider gears. After you get one side set, put the cross shaft and spider gears on the other half and do the same thing. It almost never takes .100 of shim to make this right. If you put too thick of a shim in, what you are doing is wedging the spider gear teeth together which will seriously decrease the life of the unit.

As far as the cones “screwing” into the case to increase preload because they are threaded, that is not how it works. The threaded grooves in the cones are for lubrication, that’s all. If they were there to “screw” the cone into the case, one cone would have to be threaded in the opposite direction and it would matter which side of the case they were installed on. Also, if the cones screwed into the case causing the preload to increase, it would show largely different readings forward and backwards on a breakaway torque test at the end of the axle.