Bearing Lubrication: Grease vs Oil
- Distinguish between maintenance requirements for oil-bath and grease-lubricated hubs.
- Perform a manual bearing pack using the palm-loading method to ensure complete roller lubrication.
- Verify lubrication intervals and grease specifications according to manufacturer requirements.
- Grease packing machine — Pack bearings with grease more efficiently than manual methods if available.
- Rubber plug removal tool — Access the fill hole on oil-bath hub caps to add hypoid gear oil.
- Cleaning solvent and towels — Remove all old grease from the hub and bearings prior to repacking.
Oil hubs: fill with high-quality hypoid gear oil to the level on the clear oil cap, through the rubber plug hole.
Grease hubs: replace grease every 12,000 miles or 12 months, whichever comes first. Machine-pack if possible.
How It Works
Oil Hub Level Management
Oil hubs utilize a clear cap to allow for visual inspection of the lubricant. The hub must be filled with high-quality hypoid gear oil through the rubber plug hole until the oil reaches the level indicated on the clear oil cap.
Grease Service Intervals
Grease-lubricated hubs require periodic maintenance to prevent bearing failure. The grease must be replaced every 12,000 miles or 12 months, depending on which limit is reached first.
Manual Packing Technique
Effective lubrication requires forcing grease into the internal rollers. This is achieved by pressing the widest end of the bearing into a pile of grease in the palm, repeating the process around the entire circumference until the bearing is fully packed.
Step-by-Step Procedure
0/5 doneGrease spec
| Consistency | NLGI No. 2 (lithium complex) |
Diagnostic Chart
| Symptom | Check | Spec / Expected | Likely cause & fix |
|---|---|---|---|
| Grease appears contaminated or has reached service limits. | Review service records for mileage and time intervals. | Replace grease every 12,000 miles or 12 months, whichever comes first. | The lubricant has reached the end of its service life per the manufacturer schedule. Basis: Lippert Trailer Axle Owner's Manual (Rev 03.18.2014) |
| Oil level in hub cap is below the indicated line. | Inspect the clear oil cap level and check for leaks at the plug or seal. | Fill to the level on the clear oil cap. | Low oil volume due to seepage or lack of maintenance. Basis: Lippert Trailer Axle Owner's Manual (Rev 03.18.2014) |
| Uncertainty regarding grease compatibility. | Compare the grease container label against the manufacturer's required consistency and base. | NLGI No. 2 (lithium complex) | Use of incorrect grease type could lead to premature bearing wear. Basis: Lippert Trailer Axle Owner's Manual (Rev 03.18.2014) |
| Bearing rollers appear dry despite grease being present in the hub. | Inspect the internal rollers of the bearing for grease penetration. | Force grease into the rollers until fully packed. | Bearing was not properly machine-packed or palm-packed to reach the internal rollers. Basis: Lippert Trailer Axle Owner's Manual (Rev 03.18.2014) |
At the Bay: Diagnose the Case
CASE 1 / 4
Grease appears contaminated or has reached service limits.
- Test
- Compare
- Correct
Select the next check
Basis: Lippert Trailer Axle Owner's Manual (Rev 03.18.2014). A likely cause is a hypothesis; confirm it with the applicable service procedure before repair.
Common Bay Mistakes
- ✕ Adding new grease over old, contaminated grease without cleaning the hub.
- ✕ Filling oil hubs without referencing the level line on the clear cap.
- ✕ Neglecting the 12-month interval because the 12,000-mile limit hasn't been reached.
- ✕ Applying grease only to the outside of the bearing instead of forcing it into the rollers.
- ✕ Using a grease that does not meet the NLGI No. 2 lithium complex specification.
Quick Check
Practice only — not scored.
Plan the Service Sequence
Planning practice only. Follow the applicable manufacturer's instructions, employer safety program and qualified supervision on real equipment.
Plan the first action. Compare the service steps with the bay mistakes.
Hands-on: Shop Test Equipment
Dial Indicator — Bearing End Play
Magnetic-base dial indicator (0.001 in) on the hub face, spindle nut adjustment
🛠 Equip your bay for this test →Symptom: Bearing service — set end play after repack.
Spec limits used
- 0.001–0.010 in — Allowable end play, double-nut wheel end (Dexter 9-15K service manual, p.64)
- 0.008 in — Nev-R-Lube 50 mm max axial end play (Dexter 059-831-00)
- illustrative only — Face runout limit (General shop practice)
Simulated readings for practice. Always follow the manufacturer's procedure and values on a real trailer.
Source: Lippert Trailer Axle Owner's Manual (Rev 03.18.2014) — 6