I have a 2003 navigator with 110k on it i changed the trands filter and trans oil but it shifts in to 1st gear at 4000rpms and after thats its fine till i slow down and the trans oil dissapearing with no leaks what coud it be ?????

It worked fine before? It's possible you didn't get the filter installed properly, is the sealing ring in place? Or, you could have jarred some crud loose when changed the filter. Do you have any idea how much fluid you got out of the trans, I usually measure the waste oil so I know about how much to put back in. Try shifting it manually through the gears a couple times sometimes that helps. If the fluid is not running on ground, the only other place it can go, is in the radiator. Good Luck!