{
  "slug": "wheel-seal-leaks-and-replacement",
  "title": "Wheel Seal Leaking? Steer and Drive Axle Hub Seal Replacement",
  "description": "What a leaking wheel seal looks like on a truck's steer and drive axles, what hub oil seal replacement involves, and what the record should show.",
  "track": "maintenance",
  "kind": "article",
  "isRegulatoryAdjacent": false,
  "publishedAt": "2026-10-22",
  "cfr": [],
  "related": [
    "semi-truck-and-trailer-tires",
    "trailer-wheel-end-maintenance",
    "semi-truck-brake-inspection",
    "recording-a-tire-and-wheel-service",
    "semi-truck-tire-pressure-and-inflation",
    "truck-tire-tread-depth-and-condition"
  ],
  "topics": [
    "tires_wheels"
  ],
  "nextStep": {
    "kind": "related",
    "target": "recording-a-tire-and-wheel-service",
    "text": "See what to record when a wheel seal is replaced"
  },
  "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": "2026-10-22",
    "reviewedEdition": null,
    "reviewedText": "Reviewed 2026-10-22"
  },
  "url": "https://shopbluecollarparts.com/kb/wheel-seal-leaks-and-replacement",
  "markdownUrl": "https://shopbluecollarparts.com/kb/wheel-seal-leaks-and-replacement.md",
  "body": "**A leaking wheel seal shows up as lubricant where it should not be: on the inside of the wheel, on the brake parts behind it, or on the tire.** The seal sits at the back of the hub. It keeps the hub's oil or grease in and keeps water and dirt out. This page covers a tractor's steer and drive axles. For trailer hubs, see [trailer wheel end maintenance](/kb/trailer-wheel-end-maintenance).\n\n## How are steer and drive wheel ends lubricated?\n\n- **Steer axle hubs** are lubricated with oil, semi-fluid grease or grease, depending on the hub. An oil-filled steer hub usually has a hub cap with a window that shows the level.\n- **Drive axle wheel ends** are usually lubricated by the axle's own gear oil, which reaches the wheel bearings from the differential housing. The wheel seal holds that oil in at each end of the axle.\n\nConfirm which lubricant a hub uses before servicing it, from the axle or hub manufacturer's documentation.\n\n## What does a leaking wheel seal look like?\n\nSigns to look for and record:\n\n- oil or grease on the inner face of the wheel, the brake drum or rotor, or the tire;\n- lubricant on the brake shoes, linings or pads. Record it, and handle the brake parts as the brake manufacturer's documentation directs. See [semi truck brake inspection](/kb/semi-truck-brake-inspection);\n- on an oil-filled steer hub with a window, a low level, or lubricant that looks milky, a sign of water getting in;\n- on a drive axle, a gear oil level in the differential that keeps dropping with no other leak found;\n- dirt caked onto a wet patch behind the hub.\n\nWhere the lubricant shows helps tell a seal leak from a leak somewhere else. Lubricant on the inboard side, behind the hub, is consistent with the wheel seal. Lubricant on the outboard face of a drive hub, at the axle shaft flange, is consistent with the axle flange gasket. On an oil-filled steer hub, a hub cap leaking at its gasket or fill plug is a third possibility. Seal makers publish guides to identifying a leaking seal. One example is ConMet's *Quick Reference Guide, Wheel Seal: Leakage Identification* (Part No. 10085656A, 03-2020), on ConMet's [wheel end literature page](https://conmet.com/literature/wheel-ends/).\n\n## What does hub oil seal replacement involve?\n\nReplacing a wheel seal means taking the hub off the spindle, so the work involves more than the seal:\n\n- **Bearings and races** are exposed. Inspect them, and replace them if the bearing manufacturer's guidance calls for it.\n- **The seal bore and the spindle or wear surface** the seal rides on are inspected and cleaned. Some seals ride on a wear sleeve that is replaced with the seal.\n- **The new seal** is installed with the tool and method its maker specifies, square to the bore. Seal makers publish installation instructions for each seal line. Examples are STEMCO's [hub seal installation instructions](https://www.stemco.com/resource/guardian-hp-hub-seal-installation-instructions/) and ConMet's wheel seal installation instructions on its [wheel end literature page](https://conmet.com/literature/wheel-ends/).\n- **Bearing adjustment** is set again after the hub goes back on. Use the hub or axle manufacturer's procedure for that hub. Some hubs use a pre-set bearing system and others a conventional adjusting nut. This page does not give an adjustment or torque value.\n- **Lubricant** is refilled to the level the hub or axle manufacturer specifies, and the hub is checked for leaks after a run.\n\nThe Technology & Maintenance Council (TMC) of the American Trucking Associations covers this work in RP 622, *Wheel Seal and Bearing Removal, Installation, and Maintenance*, and RP 618, *Wheel Bearing Adjustment Procedure*. Use the current revisions.\n\n## Can a removed seal go back in?\n\nOnly if the seal maker says so. Follow the seal maker's instruction for the seal on that hub. Its installation document is the authority on whether a seal that has been removed may be reused.\n\n## What the record should show\n\n- which axle and side;\n- what was found: where the lubricant was, the lubricant level and condition, and any contamination of the brakes;\n- the lubricant type, and the amount added or the level set;\n- the seal, bearings, races and wear sleeve replaced, with part numbers;\n- the bearing adjustment method, pre-set or adjusted, and that the manufacturer's procedure was followed;\n- a check for leaks after the repair.\n\nSee [recording a tire and wheel service](/kb/recording-a-tire-and-wheel-service) for how this fits the rest of the record.\n\n## Log the work in Blue Collar Parts\n\nA technician who replaces a wheel seal can log the work 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 wheel seal service in general terms. It is not a service manual and does not establish regulatory compliance. Use the axle, hub, bearing and seal manufacturers' current documentation for specifications and procedures.*",
  "license": "CC BY 4.0",
  "licenseUrl": "https://creativecommons.org/licenses/by/4.0/"
}