GM Service Manual Online
For 1990-2009 cars only

When to Check Lubricant

It is not necessary to regularly check rear axle fluid unless you suspect there is a leak or you hear an unusual noise. A fluid loss could indicate a problem. Have it inspected and repaired.

All axle assemblies are filled by volume of fluid during production. They are not filled to reach a certain level. When checking the fluid level on any axle, variations in the readings can be caused by factory fill differences between the minimum and the maximum fluid volume. Also, if a vehicle has just been driven before checking the fluid level, it may appear lower than normal because fluid has traveled out along the axle tubes and has not drained back to the sump area. Therefore, a reading taken five minutes after the vehicle has been driven will appear to have a lower fluid level than a vehicle that has been stationary for an hour or two. Remember that the rear axle assembly must be supported to get a true reading.

How to Check Lubricant

2500HD with 6.0L


Object Number: 1861346  Size: B3

All Other Series and Engines


Object Number: 1651483  Size: B3

To get an accurate reading, the vehicle should be on a level surface.

    • For all 4.3L, 4.8L and 5.3L 1500 Series applications, the proper level is 0.04 inches to 0.75 inches (1.0mm to 19.0mm) below the bottom of the filler hole, located on the rear axle. Add only enough fluid to reach the proper level.
    • For all 6.0L 1500 Series applications, the proper level is from 0.6 inches to 1.6 inches (15mm to 40mm) below the bottom of the filler plug hole, located on the rear axle. Add only enough fluid to reach the proper level.
    • For all 6.0L 2500HD Series applications, the proper level is from 0 to 0.5 inches (0mm to 13mm) below the bottom of the filler plug hole, located on the rear axle. Add only enough fluid to reach the proper level.
    • For all 6.6L DURAMAX DIESEL 2500HD Series applications and all 3500 Series applications, the proper level is from 0.6 inches to 0.8 inches (17mm to 21mm) below the bottom of the filler plug hole, located on the rear axle. Add only enough fluid to reach the proper level.

What to Use

Refer to the Maintenance Schedule to determine what kind of lubricant to use. See Recommended Fluids and Lubricants .