So I just bought a new 12v, it's a 96 and the tranny has been acting funny lately, it will shift out of first at like 2-3 miles an hour and then slip for a sec and then shift to second. Some days it will do this and others it just drives normal like it never had an issue. I'm assuming it's a loose electrical connection or something but I went through underneath briefly and didn't see anything suspicious. Also the previous owner installed some sort of **** in the cab and it can adjust the shift points, does anyone know what that is called? Any help with the tranny issue on what it could be?

 

The **** is most likely a potentiometer. It takes the place of you throttle position sensor that is attached to the throttle linkage on the fuel pump. This gives you the ability to change your shift points and the speed that your converter locks up, as opposed to the throttle position sensor doing it automatically based on throttle position. I put one on my tuck not long ago. As for the shifting problem, both transmissions I've had so far have done that under light throttle. My understanding is that the first thing you should check is all your line pressures, but I never got the chance to do that yet.