Bottom Line
Wheel End Maintenance
Wheel Ends
Wheel end maintenance, currently a necessary evil, may soon become as much a part of trucking history as solidly mounted seats and twin stick transmissions.

Factory supplied wheel ends, containing carefully assembled seals, bearings and adjusting nuts, need no periodic maintenance. "These unitized and pre-adjusted wheel end systems are similar in appearance to standard wheel end systems," according to TMC Recommended Practice RP640. It continues, "Therefore, it is important to carefully inspect the hubcap, axle shaft end and retaining nut for system identification." There should be a label or identification plate stating: "Warning: Removal Voids Warranty," "Caution: Removal of Long Life Bearings will Void Axle Warranty" or "Warning: Do Not Service Hub and Bearing System." If there is no label, you have an older design.

If you are buying a new truck or selecting between several used ones, try to specify unitized, factory assembled wheel ends. They will save you a great deal of work, and could help prevent accidents.

Most existing wheel end assemblies are not unitized. They still require periodic servicing and it is absolutely critical that adjustments must be within a specific range. The assemblies contain a seal to hold lubrication in the parts that rotate with the wheel. They consist of two single row, widespread, tapered roller bearing assemblies and an adjusting mechanism, which is a single nut held in place with a cotter pin, a tang-type locking adjustment nut or a spindle washer-type adjustment nut. Each has a method for preventing the nut from backing-off once adjustment is made.

When wheel ends are out of adjustment or seals are not correctly seated, dire consequences result. Leaky wheel seals can allow bearings to run dry. Without proper lubrication bearings can freeze on the axle, score or burn through it. The result will be the wheel assembly separating from the truck. The separation has the potential to cause damage to other vehicles, severe injury or, in far too many cases, death.

Adjustment nuts that are too tight can squeeze the bearings and prevent their rotation. This too, can score or burn axles, with the same unfortunate result. If the nuts are too loose, wheel wobble could cause irregular tire wear, cocking of the bearings, spindle damage and wheel separation. When bearings or seals are not properly installed, it is almost impossible to get accurate adjustment at the nut. Even if torque readings are correct, dimensions will be off. We're not talking about huge amounts. Tolerance for end-play at the edge of the brake drum is often only .001 inch to .004 inch.

Problems start when seals and bearings are removed. Seals are manufactured to extremely close tolerances, and care must be taken to install them properly. Installation, according to TMC RP622 ("Wheel Seal and Bearing Removal, Installation and Maintenance"), starts with handling and storage.

Here are the procedures to be followed when you R&R (remove and replace) seals and bearings:

  1. Use a crow's foot pry bar to gently remove the old seal from the hub bore. If there is a wear sleeve on the spindle, remove it by striking the face with the round end of a ball peen hammer. Never use a chisel or sharp tool that could damage the spindle. Discard the seal. Never re-use a seal.

  2. Remove the bearing cup, following the hub manufacturers' procedures. Use a bearing puller if available, or a soft steel pry bar. Do not use hardened tools. If the hub is aluminum, extreme care must be taken not to damage components. Aluminum hubs can be heated to 250 to 300 degrees to expand the hub. Higher temperatures will weaken the material. Do not use a torch, which can heat unevenly and weaken the metal. You can tell if the hub is up to temperature by testing with special temperature-sensitive wax markers. Be careful bringing the heated hub to a press. Press the cup out.

  3. Remove and clean the bearing with a filtered petroleum distillate solvent. Never use steam or water, because parts will rust very quickly. Dry the bearing using dry compressed air. Do not spin the bearing while drying it.
    Now inspect the bearings. If they show signs of rust or pitting, or if cages are the least bit damaged, replace them with new bearings and discard the damaged ones.

  4. All parts that come in contact with the bearing should be thoroughly cleaned with solvent, dipped in clean axle lubricant and placed in protective oilpaper. If none is available, use clean, dry shop towels.

  5. Installation is affected by the condition of the hub bore and the spindle, the preparation of the seal, the tools used for installation and the adjustment of end play. Start by making sure surfaces that will contact the new seal are free of rust, scale, old sealant, and any nicks, burrs or roughness that might interfere with a good seal. If scrapers are used, make sure they are softer than the hub material. Use non-metallic tools on aluminum hubs. Make sure there are no sharp edges on the bore entrance. If there are, use an abrasive cloth to remove them, then thoroughly re-clean the entire area. Be sure all old lubricant and any abrasive residue is removed.

  6. Next, prepare the spindle. Thoroughly clean it with solvent and dry it with a clean shop rag. Remove any foreign material, then use crocus cloth to polish the spindle where it contacts the seal. Clean threads and keyways with a wire brush, to remove contaminants and prevent false torque and adjustment readings. Remove sharp edges. Wipe down the spindle.

  7. If the sealing system uses an axle ring or wear sleeve, put a thin coat of non-hardening sealant on the axle shoulder.

  8. When replacing bearings, replace both cup and cone as a matched set. If new bearings are used, do not remove the rust preventive coating before installation. Also, do not remove any protective coating from new seals, if there is any.

  9. Check seal manufacturer's instructions regarding lubrication. If needed, use a light film of wheel end lubricant.

  10. Bearing cups should be pressed into ferrous hubs using the proper driver tool, sized for the particular hub. There is no one-size-fits-all tool when replacing bearings. Aluminum hubs should again be oven heated to 250 to 300 degrees. The bearing cup should be coated with a liquid, graphite-based lubricant, such as Lubri-Kote or its equivalent.
    To seat the bearing cup, use a cup driver of the right size and, with hand pressure, seat the cup squarely against the shoulder. Do not hammer the driver. If the cup is even slightly cocked, you can ruin the hub, the bearing, or both. Repeat with the other bearing cup. Then lubricate both inner and outer cups with axle oil and mate the new bearing cones with their cups.

  11. After installing the bearings and inspecting the bore, spindle and wear ring (if applicable), it's time to install the seal. Tools and procedures vary widely between manufacturers, so you should be sure to follow their instructions and use their tools. Again, installation tools are product specific.
    To install a hub-mounted seal, place the hub assembly on a flat surface. With the correct tool, adapter and bearing pilot close at hand, pre-lube the seal if necessary, using the same lubricant to be used in the hub. Place the oil seal on the tool, air side on the adapter. Follow manufacturer recommendations for specific insertion procedures. Once squarely in place, drive the seal in using firm hammer strokes. Make sure the inner bearing rotates freely.
    Many seals can be installed without a driver tool. To hand install a seal, lubricate the seal inside and outside diameters and the bore of the hub. Hand press the seal evenly into the bore. You can use a rubber mallet to gently tap the seal into place, only if recommended by the manufacturer. Avoid cocking the seal. Be sure it is evenly seated and bottomed in the bore.
    To install a spindle-mounted seal, place the seal onto the spindle so it has the "Oil Side" marking facing the spindle end. You must have the proper tool to spindle-mount a seal. Use the tool to seat the seal until the tool bottoms out. Rotate the tool and repeat to make sure the seal is properly seated. Pre-lube the inner bearing and insert it on the spindle.

  12. You are now ready to re-assemble the hub. Use a new gasket and attach the hubcap to the hub. Torque all fasteners to factory specifications, which may vary from manufacturer to manufacturer.

Next month, we'll continue with an examination of TMC's

Paul Abelson serves Land Line as technical editor and freelances from his office in Lisle, IL

Proper seal storage

  1. Keep seals away from electric motors, welders or any other ozone sources. Ultra-violet light from fluorescent fixtures or direct sunlight can also attack the polymer seals.
  2. Store seals and bearings in a cool, dry place. Do not expose them to extreme dryness or dampness.
  3. Keep them in original factory packaging until ready to use. Never store them in open bins, exposed to dust and contamination.
  4. Never hang seals or bearings on hooks or tag them using wire through their inside diameters. The metal will damage the precision surfaces.
  5. Cleanliness is critical. Wash your hands before handling seals or bearings.
  6. Avoid dropping them. Although not apparent to the eye, internal damage will affect performance. Do not use seals or bearings that have been dropped. Remember, tolerances are below 0.005 inches.