Truck Forums - Tachometer

I have a 1990 Ford F-250 diesel. My tach don't work and my automatic trany will not shift automatically. I need to shift it manually. Someone told me that the tach is the brain to the trany and it tells it when to shift. I replaced the tachometer sensor but still had no luck in repairing it. I feel the problem may be in my wiring. Does anyone know of a way of using a jumper wire to fix my problem? Thank you