Packing wheel bearings on a full-floater rear axle was a method of trying to keep from overloading hub seals with rear end lube. The grease-packed bearings also remained lubricated if the rear end grease level got low enough that it would not flow down the axle tubes and keep the hub bearings wet.

The big rigs we used to do electrical work on back in the 50's and 60's all had preventative maintenance programs that included rear wheel bearing packing at regular intervals. The service managers we dealt with insisted it resulted in fewer blown-out rear hub seals and less brake contamination with rear end grease if the bearings got packed regularly. Some of the hubs actually had an inner seal that fit around the axle shaft to keep the gear lube inboard of the hub bearings. Those hubs definitely needed grease-lubed bearings.
Jerry

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