Sure Grip

Based on what I've been reading regarding shortening axles, I think the shop will want the suregrip assembly completely disassembled. I believe the shaft that they want to run through the housing passes through the carrier bearings and is used to true-up the housing ends as they are resinstalled on the axle housing after shortening. This shaft will help line the bearings up to reduce parasitic losses inherent with axle end bearings being slightly misaligned. I would recommend completely disassembling the unit so that they can use their jig and do the job right.

Now, I do not know exactly how to do that. I wish I did.

Good luck.