The owners manual (and Haynes) specifies Mercon ATF which is supposed to be stamped on the dipstick. Mercon V is an upgraded version of Mercon fluid that can also be used in our ATX:
Product Application:
Havoline Automatic Transmission MERCON V is approved against Ford's MERCON V and MERCON service fill specifications and can be used for all Ford transmissions requiring MERCON V or MERCON fluids. It is also approved against the General Motors DEXRON-III and Allison C-4 specifications, and can be used in all applications requiring these fluids...I have used Quaker State 4x4 synthetic fluid for Mercon, Mercon V and Dexron 3 applications on my last 3 changes with good results. On my last change I used a 50/50 mix with full synthetic trick shift, but have not noticed much difference.
More details on Mercon V:
http://thegenesisnetwork.equilon.com/gen...d%20MERCONV.pdf
