2010 GMC Sierra 1500 Crew Cab Owner's Manual - Page 516

Four-Wheel Drive Lubricant checks in this section also apply to these vehicles. How to Check Lubricant Transfer Case When to Check Lubricant It is not necessary to regularly check transfer case 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. Electric Shift Transfer Case A. Fill Plug B. Drain Plug 6-56