how do change the transmission fluid in a 2004 mercury mountianeer

A 2004 Mercury Mountaineer DOES NOT have a transmission dipstick for a very specific reason. Ford does not want ''Joe is Garages'' topping up with the incorrect specification of fluid, thereby cutting down on warranty claim costs due to failed transmissions. To drain/fill ur transmission, there is a TWO-PIECE drain/fill plug on the bottom of the transmission pan. To drain it, get ur 7/8'' or 22mm wrench, & remove the plug. To fill it, using ur wrench, hold the hex fitting & using a TX-30 Torx type socket, remove the center plug. Using a ''plunger'' type dispenser, fill the transmission with the proper Ford Mercon V fluid, until fluid runs back out. Replace plug, & run engine up to operating temperature. Remove center Torx plug again, & repeat filling procedure until fluid runs out, & the transmission is filled to spec. Hope this helps

l would like to add a bit more to what Fordgirl helped with. First l would recommend a reputable shop to have ur transmission flushed. By draining just the pan, ur only doing the fluid have the service. You will still have 4 to 5 qt of fluid still left in the torque converter. A flush service should include tapping into the cooler lines. As the fluid runs into the machine, then exact amount of fluid returns into the trans through the cooler. The transmission has a thermostatic valve to limit flow dependent on temperature. This is the most through way of taking care of ur transmission. Do not worry about the filter; it is only there for major contamination. Next is checking the fluid. First the fluid has be at the correct temperature. Specs ask for between 85 & 115 deg. At the temperature, with the center plug removed, fluid should have a light steady stream flowing out. That’s the full position. If it’s low, fill through same plug. Fluid level is critical along with keeping out contamination. It is worth the service to have it performed by a certified technician.