What the hell is the sleeve for in a semi truck hub. Read Description to skip thought the video.

This video is about pre-set hubs or LMS hubs. How to install those hubs with aftermarket axle nuts. 2007 Freightliner steer axle removal and install.
00:58 Service manuals, 1:39 My service manuals and why you should keep service manual available in shop, Some info about me as a truck trailer mechanic, 2:21 The difference between a truck trailer mechanic and a diesel mechanic, 2:45 Back to service manuals, 4:00 Using Emery Cloth, 4:37 How the wheel seal works, 5:03 Inspecting the spindle
5:26 Removing the wheel seal, 5:47 The hub, 6:03 Identifying a preset hub, 6:12 LMS hub
6:49 Knowing the hub, 7:27 Inspecting the axle nut, 9:16 Knowing how to torque the axle nut
9:32 Legal disclaimers, 10:30 Torquing the hub using an AxiLok axle nut with conventional wheel bearings, 11:02 How to torque per-set using an AxiLok axle nut, 12:07 Purpose of the sleeve
12:17 How to assemble the wheel hub, 13:39 Showing you how to properly installing the pre-set wheel hub using an aftermarket AxiLok axle nut, 17:40 Verifying the lock has engaged in the axle nut, 18:03 Cleaning the hub cap, 18:56 Brake cleaner chlorinated vs non-chlorinated. Chlorinated brake cleaner will turn to a poisonous gas when a welder is in use. Non-Chlorinated is highly flammable, 19:27 Ending of video.