Proper Wheel End Service

It’s all about knowing the components and RTB

Bearing manufactures have service information available that provides detailed cup removal and installation directions, procedures for bearing adjustment and failure analysis information. Bearing life can be greatly improved by following recommended procedures for installation and inspection.


Probably the most commonly used spindle nut system is still the double jam nut system. It is currently used on both manually adjusted and PreSet or LMS hub assemblies.

Single spindle nut systems like the Axilok or ProTorq spindle nuts are becoming more common. While the single nut systems were designed to be used for manually adjusted bearing systems, they may also be used on PreSet and LMS hub systems.

There is a significant difference in the assembly procedures for manually adjusted and PreSet or LMS bearing systems, as well as between the various spindle nut systems. This is one of the key areas where the wheel end must be correctly identified and installed per the proper instructions.

Unitized hub assemblies typically have unique spindle nut systems and assembly torque requirements that are much higher than the assembly torque for manually adjusted and PreSet or LMS hub assemblies. It is important that the correct assembly procedure be followed for proper installation of unitized hub assemblies.


Lubricants currently used in wheel ends vary from CD 50 oil up to NLGI 1, 2 and 3 greases. While PreSet and LMS hub assemblies should not be lubricated with NLGI 1, 2 or 3 greases, most unitized hub assemblies are lubricated at the factory with Grade 2 synthetic grease.

Many fleets now specify NLGI grade 00 semi-fluid grease in trailer hubs. Trailer hub manufacturers have responded and added lubricant fill plugs to the barrel of the hub to aid in installing the lubricant.

The fill volume for semi-fluid grease in trailer hubs is critical. The use of a metered dispenser is advised to insure the recommended amount of grease is installed. Installation procedures for manually adjusted hubs are described in TMC RP 631A.


In recent years, changes in wheel bearing systems, spindle nuts systems, seals and lubricants have made it mandatory that product specific service information is referenced prior to servicing wheel end components. While most of the changes have made it easier to service a wheel end, there are some specific requirements for each system that need to be identified and followed closely to insure safe operation of the vehicle.

Manufacturers have responded by making service information available in a variety of formats, including installation instructions included with the product, service manuals and online service information and training accessible through the Internet. Take advantage of the resources available and RTB (read the book) before you begin any wheel end service.

If you have any questions about a particular wheel end service requirement, contact the customer service group for the component in question for additional product support.

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