2008 Chevrolet Suburban Owner's Manual - Page 418

How to Check Lubricant To get an accurate reading, the vehicle should be on a level surface. 2500 Series A: Fill Plug B: Drain Plug 1500 Series A: Fill Plug B: Drain Plug If the level is below the bottom of the filler plug hole, located on the front axle, you may need to add some lubricant: • When the differential is cold, add enough lubricant to raise the level from 0 (0 mm) to 1/8 inch (3.2 mm) below the filler plug hole. • When the differential is at operating temperature (warm), add enough lubricant to raise the level to the bottom of the filler plug hole. 5-54