You only have 4 gears on your car. If your S3 light is flashing, your tranny is telling you it has a problem and you need to read the code to find out what it is.

The speedo cable probably broke. Just look in your engine compartment in front of your firewall, and you'll see a cable with a big nut in the middle. Separate the two cables.
Check the lower cable to see if it's broken inside.