Where do you check fluid in 1999 gmc Yukon transfer case?

To check the fluid in a 1999 GMC Yukon's transfer case, locate the fill plug on the side of the transfer case. Remove the fill plug using a wrench or socket, and check if the fluid level is even with the bottom of the hole. If fluid spills out when you remove the plug, the level is sufficient; otherwise, you'll need to add the appropriate transfer case fluid until it reaches the proper level. Always ensure to use the recommended fluid type for optimal performance.