unplug the speed sensor on the txfr case. three pins. 9vdc,ground and the other nothing. if the readings are good pull the sensor and check it over real good. it may have just died with age. it is nylon and it could have simply worn out. if it looks ok, make sure it goes back in exactly as removed.
TREAT EVERY STRESSFUL SITUATION AS A DOG WOULD.
IF YOU CAN'T EAT IT OR PLAY WITH IT,
JUST PEE ON IT AND WALK AWAY.