Meritor

P4 MM 35.02.001; 5th Generation Cascadia MM
    Notice: Failure to keep the rear axle filled to the proper level with the recommended lubricant can result in rear axle damage.
    Notice: When operating under adverse conditions, it may be necessary to change the axle lubricant at more frequent intervals than listed in the scheduled maintenance tables. Failure to do so could result in axle damage.
  1. Park the vehicle on a level surface, shut down the engine, and set the parking brake. Chock the tires.
    2. Important: Oil level must be checked at each M1 interval on Meritor axles.
  2. Clean the fill plug and the area surrounding the fill plug on the side of the axle carrier. Remove the plug. Check the lubricant level when the axle is cold, or near room temperature.
    3. Note: Some Meritor® axles have a small tapped and plugged hole near and below the housing oil fill hole. This smaller hole is for a lubricant temperature indicator only, and should not be used as a fill or level hole.
  3. Check that the lubricant is level with the bottom of the fill hole. See Fig. . If low, check for oil leaks, and correct as needed. Add oil to the level of the fill plug, using the lubricant recommended in Table .

    Table 1, Meritor Drive Axle Recommended Lubricant

    Recommended Lubricant Type

    Ambient Temperature

    Lubricant SAE Viscosity Grade

    Meritor Specification

    Synthetic Gear Oil

    –40°F (–40°C) and Up 1

    75W–90

    0–76–N

    –40°F (–40°C) and Up

    75W–140

    0–76–M
    1. There is no upper limit on these outside temperatures.

    Table 1, Meritor Drive Axle Recommended Lubricant

    • Correct (lube level at bottom of fill hole)

    • Incorrect (lube level below fill hole)

    Fig. 1, Axle Lubricant Level Inspection

  4. Install and tighten the fill plug 35 lbf·ft (47 N·m).
    5. Important: Always check the axle breather whenever checking the lubricant level. Check the breather more frequently under adverse operating conditions.
  5. Check the axle housing breather. Make sure that it is open and unclogged. See Fig. . If the breather is plugged or damaged, clean or replace it as needed.

    1. Axle Housing Breathers

    2. Carrier Oil Fill Plugs

    3. Interaxle Differential

    Fig. 2, Meritor Axle Housing Breathers

    6. Note: When adding to or checking the oil level, make certain the hub cap and plug are clean before removing the plug; this will minimize the possibility of dirt and road grime entering the assembly.
  6. On non-drive axles using oil-lubricated wheel bearings, check the oil level at the wheels, and add oil if low. Use the same lubricant recommended for the drive axle.
Note:
Parent topic: Inspection of the Axle Breather and Axle Lubricant Level
Document Number: 0000103607
Manual Publication Date: 2025-07-14
Topic Publication Date: 2026-05-06