2009 GMC Yukon Owner's Manual - Page 449

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. Headlamp Aiming The vehicle has a visual optical headlamp aiming system. The aim of the headlamps have been preset at the factory and should need no further adjustment. However, if the vehicle is damaged in a crash, the aim of the headlamps may be affected and adjustment may be necessary. All except 1500 Series A: Fill Plug B: Drain Plug If oncoming vehicles flash their high beams at you, this may mean the vertical aim of your headlamps n eeds to be adjusted. • 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. 5-53