Hello. I have been all around with the problem. Most times it is the circuit board, then the speedo, then the connections to tranny. However, I would check the ABS brake system while driving the car. You may have an intermitant speed signal that won't light the ABS light, but will act up at the tranny end. The speed signal goes to the ABS computer then to the speedo then to the tranny computer, so I would check it in order of signal. That is the best I can tell you.