Cable-driven and pulse-generator speedometers can read short or long once tire size or gearing changes, and this Stewart Warner GPS receiver corrects for that by calculating true ground speed from satellite data instead of a mechanical or magnetic pickup. It is designed to slot directly into compatible Stewart Warner electric speedometers.

Stewart Warner M-988P Compatibility Notes:

• Outputs 8,000 or 16,000 pulses per mile to match the connected speedometer.
• Provides true ground speed independent of tire size or axle ratio.
• Compatible with Stewart Warner Wings, Power Series, and Green Line speedometers.
• Also works with Deluxe speedometers scaled to 120 MPH or higher.
• 12 volt DC operation.