So I just got an 02 dakota 3.9 4x4 with 39,124 miles from the county for $1250. the engine runs like a chap but the transmission won't shift. I changed the speed sensor which brought it out of limp mode but now it won't downshift at all unless I do it manually. All the gears are there but it will start out in 3rd from a stop unless I put the shifter in first. Any ideas?