yesterday I backed out of the garage and proceeded to the stop sign down my street, and the speedometer said I was going 37 miles an hour! I was probably going 15 mph! What happened

Hello, This is likely a failed vehicle speed sensor, or there may be damage to the vehicle speed sensor circuit. Have it scanned by a professional to identify any inconsistent data, but know that the ABS control module or body control module may have just had a little fluke.