fords vehicles overdrive is different 1999 expedition/1995 contour?

[Jess/19]

both of the cars i've listed does this why do ford vehicles goes into overdrive different like it depends on how hard you're pushing the accelerator like if you are really on the accelerator it goes 1st 2nd 3rd then overdrive like a regular vehicle but if your not pressing the accelerator that much at take off it goes 1st 2nd then some other gear then overdrive its like 3rd and overdrive just goes in together does anyone else notice this on ford vehicles