The recommended fluid change interval is 60,000 miles. If you are weary about working on your truck do this maintenance procedure. It is easier than shucking corn in a hen house and will boost your confidence.
What you will need
*10mm hex (Socket or Allen Key)
*3 quarts of Mercon ATF
*1/2 Socket to take skid plate off.
. Gather your tools/supplies and locate the transfer case. Notice the two plugs.
. Get your funnel and oil catcher in place then remove the bottom drain plug. Remove top fill plug while draining or after draining. Catch the draining fluid in the funnel to route it to your oil catch pan. If you do not do this you will make a mess. The cleanest way is to do Option 2.
Step 2 Optional
. I removed the transfer case skid plate. This makes it easier and cleaner while the fluid drains. I put a coat of paint on the plate while it was out. If you remove the skid plate you will need a 1/2 socket and ratchet, or alike tool.
. After the fluid is finished draining, replace the bottom drain plug.
. The fluid calls for Mercon ATF. If it is Mercon compatible you are good to go. I used some Advance Auto Mercon since I had some left over, but this pic is Mercon SP which is fine. Notice the squirt cap. You will want one. It is a lot easier than a funnel.
Now stick the cap in the fill hole and squirt the fluid in until it pours out of the fill hole. This will take approximately 2.5 quarts. Replace the fill plug.
Put some miles on the truck, check for leaks and check the fluid level. Top off if needed.