hey guys, i have a 2004 ranger edge 4x4 with the 3.6 litre motor and automatic tranny. everything works fine on it, and it seems to shift into everything else fine. when i hit the overdrive button and im cruising at 70 it tries to shift, like the rpms drop, and then go back up to about 3000, then down to 2000 and back and forth. it will continue to do that until i hit the button again. anyone have any ideas on what it might be? any help would be much appreciated, since i have to drive long distances sometimes it really sucks cruising at 3000 rpm and gets about 14mpg