Hi Ron,
This was Chryslers intermediate step to an automatic. The transmission has 4 speeds, two in each of two ranges. The shift lever operates low range and a high range. The transmission is coupled to a fluid converter with a clutch to engage and disengage the transmission. To operate you choose the range you want (usually high). Release the clutch pedal and the car will remain stationary at idle just like a modern automatic. Step on the gas and the car accelerates (rather slowly). When you reach a speed where you want to shift to a higher gear you let up on the accelerator pedal and a solenoid engages the other gear in the range you have selected. Just like an electric overdrive.
My first car was a '53 Dodge Coronet with a 241 Hemi and a gyromatic.
Jim R
