I wonder if someone could explain the purpose of the crush sleeve found in so many automotive rear ends? I've been through countless different transmissions and gearboxes over the years, many of which use tapered roller bearings, all requiring adjustments for preload in one form or another. Either a threaded adjustment nut with nylock or a castle nut with a locking pin. Some have shims under bearing cones or behind bearing cups, variable thickness snap rings, all have something to establish and maintain a desired preload. Some of these boxes transmit a great deal of power and drive some pretty large machinery, yet I've never encountered one that employed a crush sleeve between two bearing cones as well as whatever other adjustment means they employ. I can't imagine manufacturers adding that in without a valid reason.

 

1950s engineering and assembly line methods. All things being equal the crush sleeve allows for a one and done assembly. Put it together, torque it, next. Pretty simple and reliable and quick when all the parts are new and in spec. That's my theory FWIW.

 

Not sure I buy the "assembly line" aspect at all. If that were the case, then why not the "one and done" process on rebuilds as well? Seems to me achieving proper bearing preload still requires small incremental adjustments with constant measurement of rolling torque. This would be the case whether a crush sleeve is involved or not.

 

Shims require repeated disassembly and assembly to achieve preload. A crush sleeve requires a significant amount of force to deform, think of it as an adjustable stack of shims....but only adjustable in decreasing increments. Tighten the pinion nut until the correct preload is reached and done. Shims hold up better in severe applications but I have rarely seen an aftermarket crush sleeve be the failure point. Getting the correct pattern and pinion depth may require a lot of r&r doing the visual pattern method but has nothing to do with setting preload.

 

I understand that pinion shaft preload has nothing (or very little) to do with the tooth contact pattern and how that's achieved. My point is that preload can be established by tightening the pinion nut with or without a crush sleeve between the bearings. Therefore there must be another reason for it's being there.

 

While it would be true that preload can be established without shims or crush sleeves, there would be no clamp load against the pinion nut other than the bearings. The sleeve or shims physically maintain the distance at which preload reached allowing the pinion nut have some amount of torque applied to it to prevent the nut from backing off. Thread locker is more insurance to keep the pinion nut secure.

 

I think of it as a spring, holding outward pressure between the inner races.