{
  "slug": "trailer-wheel-end-maintenance",
  "title": "Trailer Wheel End Maintenance: Hub Oil, Grease and Bearings",
  "description": "Trailer wheel end maintenance covers hub oil or grease, hub seal replacement, and wheel bearing adjustment, and the difference between the two.",
  "track": "maintenance",
  "kind": "article",
  "isRegulatoryAdjacent": false,
  "publishedAt": "2026-10-19",
  "cfr": [],
  "related": [
    "semi-trailer-maintenance",
    "air-brake-system",
    "trailer-abs-module",
    "semi-truck-brake-inspection"
  ],
  "topics": [
    "tires_wheels",
    "chassis_trailer_body"
  ],
  "nextStep": {
    "kind": "start",
    "target": "/start",
    "text": "See how wheel-end service is recorded for your customer"
  },
  "sources": {
    "citations": [],
    "bcpRole": "Blue Collar Parts records the work and sends the report to your customer. It does not perform, certify or approve inspections.",
    "reviewed": "2026-10-19",
    "reviewedEdition": null,
    "reviewedText": "Reviewed 2026-10-19"
  },
  "url": "https://shopbluecollarparts.com/kb/trailer-wheel-end-maintenance",
  "markdownUrl": "https://shopbluecollarparts.com/kb/trailer-wheel-end-maintenance.md",
  "body": "A trailer wheel end carries the trailer's weight on a hub, a pair of bearings, and a seal that keeps the lubricant in and contamination out. Wheel end maintenance is checking and servicing those three things before a seal fails or a bearing runs dry.\n\n## Hub oil or grease\n\nA trailer hub is lubricated one of two ways, and the two aren't interchangeable:\n\n- **Oil-lubricated hubs** hold a reservoir of oil, visible through a sight glass or window on the hub cap, that bathes the bearings as the wheel turns.\n- **Grease-lubricated hubs** pack the bearings and the hub cavity with grease instead, with no oil level to check.\n\nA hub built for oil cannot simply be filled with grease, or the reverse — the seal, the bearing set, and the hub cap are matched to the lubrication type. Confirm which type is on the trailer before servicing it, and use the hub manufacturer's documentation for how much to use and how to check the level, since that value differs by hub model and axle rating and this page does not state one. The axle and hub makers — ConMet, Meritor, Dana/Spicer, Hendrickson and SAF-Holland among them — publish that specification for their own hub lines.\n\n## Hub seals\n\nThe hub seal keeps lubricant in the hub and water, dirt and road debris out. A seal that leaks, that's been installed with the wrong driver or at an angle, or that's been run dry shows up as oil or grease at the wheel, a discolored or low sight glass, or contamination found at a later teardown. Seal makers such as Stemco publish the installation specification and tooling for their own seals; follow the seal manufacturer's documentation for the seal actually on the trailer, including bore and spindle preparation, because a seal installed against the wrong spec fails again quickly.\n\n## Wheel bearing adjustment\n\nWheel bearing adjustment sets how much the bearing can move on the spindle: too tight and the bearing runs hot and wears quickly; too loose and the wheel can wobble and the seal can fail early. Some trailer hubs use a pre-set, pre-adjusted bearing system that sets this at the factory or at hub assembly and is not adjusted by hand in service; others use a conventional adjusting nut that's torqued and backed off to a specified setting. Which kind is on the trailer, and the torque or end-play value for it, is published by the hub or axle manufacturer for that model — this page does not give a number, because the correct one depends on the specific hub and bearing on that axle. Confirm it against the manufacturer's documentation for the hub's serial number or build before adjusting.\n\n## When to replace instead of service\n\nA hub, bearing or seal that's been run hot, run dry, or contaminated is often a replacement rather than a re-service, even if it still turns freely by hand. The manufacturer's documentation for the hub says what condition calls for replacement versus continued service.\n\n## What should the service record show?\n\nA record of trailer wheel-end service should show:\n\n- which axle and side, and whether the hub is oil or grease lubricated;\n- the lubricant used and the level or condition found;\n- seals and bearings replaced, with part numbers and the hub or seal maker's specification followed;\n- the bearing adjustment method (pre-set or adjusted) and the result the manufacturer's procedure called for;\n- anything found on the way in: leaking seal, contaminated lubricant, heat discoloration.\n\nA record kept by the trailer's own unit number or VIN stays with the trailer, whichever tractor pulled it.\n\n## Log the work in Blue Collar Parts\n\nA technician who does this work can log it in Blue Collar Parts and send the record to their customer, who confirms it. [Learn what Blue Collar Parts is](/kb/what-is-blue-collar-parts).\n\n---\n\n*This page describes trailer wheel end maintenance in general terms. It is not a service manual and does not establish regulatory compliance. Use the equipment manufacturer's current service documentation for equipment-specific specifications and procedures.*",
  "license": "CC BY 4.0",
  "licenseUrl": "https://creativecommons.org/licenses/by/4.0/"
}