2006 Chevrolet Avalanche Owner's Manual - Page 402

If the level is below the bottom of the filler plug hole, located on the front axle, you may need to add some lubricant: Bulb Replacement For the proper type of replacement bulbs, see Replacement Bulbs on page 5-60. For any bulb changing procedure not listed in this section, contact your dealer. • When the differential is cold, add enough lubricant to raise the level from 1/2 inch (12 mm) to about 5/8 inch (18 mm) below the filler plug hole for the 1500 series, and from 1/4 inch (6 mm) to about 3/8 inch (10 mm) below the filler plug hole for 2500 series. Halogen Bulbs • When the differential is at operating temperature (warm), add enough lubricant to raise the level to the bottom of the filler plug hole. {CAUTION: Halogen bulbs have pressurized gas inside and can burst if you drop or scratch the bulb. You or others could be injured. Be sure to read and follow the instructions on the bulb package. What to Use Refer to the Maintenance Schedule to determine what kind of lubricant to use. See Recommended Fluids and Lubricants on page 6-13. 5-52