Spinning With Bearings
- Kopycinski’s Brain

Most all the spinning parts on our vehicles would simply not function well without one simple invention—bearings. You’ll find them in the engine, transmission, transfer case, and axles. Bearings allow shafts to spin in housings and transmit power throughout the entire drivetrain, reducing friction while riding in grease or oil.

There are three common types of moving bearings used in automotive drivetrains: needle, ball, and taper roller bearings. Each has an intended use and the sizes used are dependent on torque load, supported weight, and rotational speed. They typically consist of an inner race, outer race, and a set of rollers or balls in a cage that ride between the two races.

Bearings can support shafts in two directions, radially (perpendicular to the shaft) and axially (parallel to the shaft). Needle bearings support loads almost entirely in a radial direction due to the cylindrical shape of the rollers. Ball bearings support most loads in a radial direction and can support light loading in an axial direction. Tapered roller bearings with their angled rollers are designed to support heavy loads in both directions.

The three types of bearings are designed to support different types of loading. Needle bearings (Top Right) are commonly found in tight spaces on shafts in transmissions or transfer cases, or in U-joints, where little or no axial loading is present on the bearing. Ball bearings (Bottom Left) are often found in transmissions, transfer cases, and at the outer axle shafts on rear semi-floating axles. Taper roller bearings (Bottom Right) are most commonly found in use for wheel bearings or in differentials.

Grease (or an oil bath) is the lifeblood of a bearing. When lubrication is lost or compromised, surface friction causes rapid heating. Heating degrades the treated metal surfaces of the bearing and rapid wear and failure ultimately follows. Contaminants like water or dirt can hamper the lubricant’s ability to work. Keep bearings clean and dry. Many bearings can be lubed quickly with a bearing packer, such as this. Or use the original method of hand packing by working grease thoroughly into the bearings with your fingers.

The separate outer races or inner portion of taper roller bearings or ball bearings often have a press fit to the housing they ride in. Bearings or races to be discarded can be driven out using a steel rod or other drift. Ideally, though, install new bearings using a softer brass drift to prevent marring or distorting the race or bearing during installation.