Refer to the Maintenance Schedule to determine how often to check the lubricant. See Scheduled Maintenance .

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

If you have the 1500 Series, the proper level is from 5/8 inch (15 mm) to 1 5/8 inch (40 mm) below the bottom of the filler plug hole. The proper level for the 2500 and 3500 Series is from 0 to 1/4 (6 mm) below the bottom of the filler plug hole. Add only enough fluid to reach the proper level.

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