I have a 99 f150 5.4 and the speedo staying jumping Friday night all over the place and wad causing the trans to keep kicking it out of overdrive but the time the speedo stops bouncing and gives me a reading it shifts fine. .I've replaced the sensor on the trans and now the one and the rear end and yet does it...what else can I do to try and eliminate this problem any input is appreciated

 

well... driving the truck now at low speeds the truck seems fine but if go any faster like freeway speeds it does horrible..ive replaced both sensors the one on the trans and the diff but yet still no change in its horrible acting up ill check fuses tomorrow after work... any input is appreciated thanks in advance