Seals & Seal Installation
- Differentiate between grease seals and oil-bath hub seals.
- Perform proper seal removal and replacement protocols to prevent damage.
- Apply correct installation techniques and lubrication to ensure a leak-free assembly.
- Seal driver — Drive the new seal in square by contacting the outer edge only.
- Seal removal tool — Remove the existing seal from the hub during disassembly.
- Clean shop rag — Clean the hub bore and spindle before installing new components.
- Lubricant — Lightly coat the seal lip before sliding the hub onto the spindle.
Grease seals keep grease in and water out; oil-bath hubs use a seal designed for liquid oil and must be leak-free.
Replace the seal any time the hub is removed. A seal that has been pulled is damaged.
Drive the new seal in square with a seal driver that contacts the outer edge only. A cocked seal leaks.
Lightly coat the seal lip with lubricant before sliding the hub onto the spindle.
How It Works
Seal Functional Requirements
Grease seals are designed to keep grease in and water out. Oil-bath hubs utilize a seal specifically designed for liquid oil and must remain completely leak-free to maintain lubrication levels.
Mandatory Replacement
Replace the seal any time the hub is removed. A seal that has been pulled is considered damaged and cannot be reused without risking failure.
Installation Geometry
The seal must be driven in square. If a seal is cocked during the installation process, it will leak. Contact should only be made with the outer edge of the seal during driving.
Diagnostic Chart
| Symptom | Check | Spec / Expected | Likely cause & fix |
|---|---|---|---|
| Leaking oil-bath hub | Inspect the seal for squareness and damage to the seal lip. | Per the applicable manual | A cocked seal or a seal installed without lubricant on the lip. Basis: Lippert Trailer Axle Owner's Manual (Rev 03.18.2014) |
| Water intrusion in grease hub | Check the condition of the seal and ensure it was replaced during the last service. | Per the applicable manual | Reusing a seal that was previously pulled or failure to drive the seal in square. Basis: Lippert Trailer Axle Owner's Manual (Rev 03.18.2014) |
| Premature seal lip wear | Verify if lubricant was applied to the seal lip during assembly. | Per the applicable manual | Sliding the hub onto the spindle with a dry seal lip. Basis: Lippert Trailer Axle Owner's Manual (Rev 03.18.2014) |
At the Bay: Diagnose the Case
CASE 1 / 3
Leaking oil-bath hub
- 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
- ✕ Reinstalling a seal that has been pulled from the hub.
- ✕ Using a driver that contacts the inner portion of the seal rather than the outer edge.
- ✕ Installing the seal at an angle (cocked) instead of square.
- ✕ Failing to coat the seal lip with lubricant before sliding the hub onto the spindle.
- ✕ Using a grease seal in an application designed for an oil-bath seal.
Quick Check
Practice only — not scored.
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) — 5