Electric speedometer

I’m using an electric speedometer from a 78SC 911, this required mounting a sensor and a magnet ring to a 901 transmission. Since factory parts are for 915 and later transmissions, I custom made these parts.

The magnet ring was machined from aluminum and fitted with 8, 1/2” round magnets and sealed with JB Weld. The inside diameter was machined to fit snuggly over a stock CV joint.

The sensor is a Cherry magnetic reed switch which provides a switch closure to drive the speedometer.

Sensor and magnet ring installed into position