I've just hit 120,000 miles and I know for a fact the transfer case oil has never been changed...should I do it or leave it alone? how often do you have to do it? what kind do you use on a 99' with the 4R70W trans?

 

Our transfer cases use Mercon ATF. It's a good idea to change it every 30,000 miles if you continue to use a non-synthetic Mercon ATF. If you use a synthetic Mercon ATF you can go longer. I'd change it now with a quality non-synthtic Mercon ATF. You'll only help it and the non-synthetic Mercon won't create any leaks by cleaning out the crud that might be creating a false seal. Whereas a synthetic Mercon MIGHT cause a leak because of cleaning the crud but then also might eventually rejuvenate the hardened seals/gaskets so they stop leaking. It's cheap and not too difficult to do .

Whimsey

 

hey thanks alot...which Mercon? would Valvoline Mercon V work? that's what I used to change the fluid in the tranny...is it the same stuff in the transfer case? and how many quarts does it take?

 

Ford recommends MERCON not MERCON V for our transfer cases even thought the auto trannies use MERCON V Ford still spec's "plain" MERCON for the transfer case. If MERCON V was ok to use you'd think that Ford would use it instead of having 2 different ATF fluids in the same vehicle . The Haynes manual says the transfer case holds 2 quarts.

Whimsey

 

Change it at 30K and use synthetic. The t-case hardly takes any fluid. It says 2 qts but my buddy just flushed my tranny and t-case for me and it didn't even take the 2. I use Amsoil and I wouldn't hesitate to do it in a truck with any mileage. Piece of mind knowing it will work, when you want it to and at any temp