SIDEBAR: Unitized Hubs

The ultimate solution to the problem of leaking seals, in some eyes, is a pre-packaged or unitized hub. The hub, seal, lubricant, and bearings are assembled together as a single unit which is set into the axle spindle, eliminating the need for bearing adjustment, seal installation, and subsequent lubrication. Con Met, Meritor, Stemco, and Dana’s Spicer Division have introduced such designs.

Unitized hubs have about 20% of the steer-axle market and some 10% of the trailer market, according to Meritor’s Kurt Burmeister. Meritor and other manufacturers promote unitized hubs as “maintenance free.” But Burmeister and other supplier reps are quick to point out that maintenance-free doesn’t mean “forget about it.”

“Our field-maintenance manual says that when the user has a trailer in for normal maintenance, the mechanic is to take a look at those wheel ends, ensure they rotate smoothly, and check for any excessive end play,” notes Jim Grant, chief engineer for Meritor trailer products. “The bearings are slightly pre-loaded, so there shouldn’t be any end play, but the point is, you do want to keep an eye on things anyway.”

Burmeister says the payback on the extra cost of a unitized hub occurs, typically, at about 250,000 miles when the first change of a conventional seal would likely be done. The estimated $250 cost of that job is about the same as the upcharge for the unitized hub.