Mid-1930s to mid-50s cars have always been my favorite cars.  Being born in 1949, I have memories of seeing those cars on the road being driven daily.  It wasnt until around 1960 when the pre-war cars were more seldom seen.  

        Along with the styling evolution from mid-30s Art Deco, streamlining, envelope bodies and the chrome rolling juke box styles of the 50s, there were a lot of mechanical innovations that were introduced, and some worked really well, making for much less labor-intensive driving.  I just covered a two-part series on Packards R-9 overdrive.  It worked well for years, evolving into the R-11, staying popular even after the Ultramatic (automatic) was introduced in 1949.  During this period, many car manufacturers were ultimately working toward an all-automatic transmission.  The goal was to make their cars easier to drive and entice women to be potential car buyers.

        So many of the car makers offered overdrives, and semi-automatics (vacuum clutches, etc.).  Oldsmobile was the first one to bring out a reliable fully automatic transmission in 1938 with GMs Hydramatic.  Packard added to the ease of driving with its Electromatic clutch introduced in 1941 and continued through 1949.  It was evidenced by a red clutch pedal until mid-48, then black through 1949.  Here is how Packard described the vacuum-electric Electromatic clutch function:

 The Electromatic clutch which is supplied as special equipment automatically accomplishes the engagement and disengagement of        the clutch.  The car is started, gears shifted and the accelerator pedal        used in the usual way, but without touching the clutch pedal.  Even when stopping, it is not necessary to touch the clutch pedal.

To lock out the Electromatic clutch  and restore the normal use of        the clutch pedal, pull out the switch knob on the instrument panel        marked Electromatic. When it is desired to return to electromatic        operation, push in the switch knob.

        The Electromatic clutch with overdrive consists of:

        1.  The Lockout Switch, located in the instrument panel, which enables the driver to select the Electromatic Clutch or lock it out at will.

        2.  The Lockout Solenoid Valve located in the clutch control valve, which is energized and de-energized manually by the lockout switch and automatically by other switches.  It locks in and locks out the Electromatic Clutch when desired by the driver, or automatically when driving conditions require it.

             *Packard Owners Manual, 1946-47

        3. The Clutch Control Valve, which regulates the partial vacuum by metering the amount of air admitted to the power cylinder and supplies the varying pressures for smooth clutch engagement.

        4. The Power Cylinder.  This device provides the force required for the degree of engagement and disengagement of the clutch as directed by the clutch control valve.  The power cylinder diaphragm is connected to the clutch relay lever by means of a cable-pulley system.

        5.  The Governor Switch, which prevents disengagement of the clutch when the accelerator is released at speeds greater than governed speed.*

        6.  The Direct Speed Switch, which is operated by the direct and second idler lever and permits shifting from high gear above governed speeds.  The direct and second idler lever mechanically closes the direct speed switch at the first movement of the shifting lever out of high gear and insures that the direct speed switch is open only when the car is in direct drive and overdrive.

        7.  The Accelerator Switch, which locks in the Electromatic, releasing the clutch only when the accelerator pedal is fully released below governed speed.