1999 Mazda 929 trans light blinks on and off and spedo stops working

Your car is equipped with a computer controlled engine management system. An independent auto service center can scan your computer for fault or error codes. The information should pinpoint the malfunctioning components. The speedometers in these cars are operated via a cable, which comes out of the glove box. If you look under the car (drivers side) you can see it. It sounds like the speedometer cable (this also causes the speedometer to stop working and also for the hold light to start flashing). Check to see if it has worked itself loose, other thing it could be is at the other end. It plugs directly into the back of the speedometer, you have to take out the dash and it is possible it may have come loose.