What's the 2001 Chevy silverado rear differential fluid type?

The recommended fluid for the rear differential in a 2001 Chevrolet Silverado 1500 is SAE 75W-90 Synthetic Axle Lubricant (GM Part No. 12378261) or equivalent that meets GM's 9986115 specifications. You should have the rear differential fluid changed about every 15,000 miles, or more if used for towing often. To drain it, You'll need to remove the drain plug on the bottom using a 3/8" ratchet, no socket is needed. Have a container below it to catch the oil. Once emptied, return the drain plug a then remove the filler plug, with the 3/8" ratchet. It is located on the passenger side of the truck, just behind the drive shaft. Fill to 5/8 inch to 1-5/8 inch below the filler plug.