NOTE: This article from the Commercial Vehicle Aftermarket Team of the Timken Co. generally references torque specifications and bearing adjustment. Always refer to the original equipment manufacturer’s recommended procedures for complete installation details.
Preadjusted Is Preferable
Most fleets follow manual bearing-adjustment methods for steer, drive and trailer axle assemblies on Class 6, 7 and 8 trucks. However, this procedure can lead to wheel-end problems when the setting is not correctly verified. As many techs are learning, there’s an easier way to achieve the proper wheel bearing endplay using preadjusted rebuild kits.
These kits use reduced-stand bearings, meaning they have tighter bearing tolerances, half the stand or measurement tolerance of standard bearings. This precise tolerancing provides for a highly accurate and repeatable setting, meaning more reliable results.
Techs familiar with both methods tend to prefer preadjusted kits for simplifying rebuilds and reducing the risk of errors.
Easy Seal Inspection
Wheel bearings can be difficult to inspect on a regular basis. Quickly check for signs of trouble by looking at the backside of the hub—slight seepage, wetness or discoloration is normal, while drops of oil or grease are not. Deal with excessive seal leakage by inspecting for bearing issues, and replace if damaged.
For this installation, you will need a torque wrench and the correct size socket for your spindle nut (it’s a good idea to double-check your socket size to ensure an EXACT fit). Always install bearings in a clean environment and keep all products in their protective wrap until you’re ready for them. Be sure to handle bearings with extra care, as components like the cage can be easily damaged. Also take time to thoroughly check all nut and spindle threads for debris that could cause excessive nut torque and inspect the spindle for excessive wear and replace if worn. Read all manufacturer installation instructions and product warnings prior to beginning installation, as instructions, torque specifications and bearing adjustments contained below are general and may differ for your product. Always follow proper safety practices.
Step 1: Mount the hub assembly onto the axle spindle while holding the outer cone in place. Make sure the bearing cones, spacer and spindle are aligned. For steer drive and trailer hubs, ensure the small end of the spacer is facing the outward side of the hub. Loosely install the inner (adjusting) spindle nut.
NOTE: Preset hub kits use a spacer between the inner and outer bearings that is NOT optional and should NEVER be thrown away. ALWAYS install a new spacer to get the best performance from the new bearings (worn spacers can cause incorrect endplay adjustment).
Step 2: Torque the inner spindle nut to 300 ft.-lbs. while rotating the hub. Do NOT back off the spindle nut.
Step 3: Install the locking device (typically a lock washer) by engaging the slot in the spindle and the dowel pin on the adjusting nut. If the pin and washer (or washer tang and nut flat) will not align, remove the washer, turn it over (flip 180°) and reinstall.
NOTE: If the locking device still does not engage, TIGHTEN the adjusting nut SLIGHTLY (contrary to manual setting methods that require loosening the nut enough for alignment).
NOTE: If utilizing a single-piece lock nut, torque to 300 ft.-lbs. and engage the locking device. If you cannot engage the locking device, then you must tighten the nut until the lock can be installed.
Step 4: Install the jam nut and torque to 200 ft.-lbs. for spindles less than 2-5/8" diameter and 300 ft.-lbs. for spindles over 2-5/8" diameter. For many multipiece or jam-nut systems, also be sure to bend the lock tab or install the set screw after the outer nut is torqued.
Wheel-end bearings that are not properly installed and maintained can experience seal failure or cause tires to wear quickly. Preadjusted hub assemblies can take the uncertainty out of manual setting procedures, helping fleet owners operate more efficiently.