When autotran is shifting at 45mph it will shift in an out of gear. on 1998 Dodge Ram 2500

If you get above 45 it will finally shift. If you keep it at the shift point of 45 mph it will shift in and out of gear. Would it be the turns output sensor? And if it is where is it located? Thanks.

Asked by for the 1998 Dodge Ram 2500