What optional two-speed rear axle helped the Model T climb hills?

The optional two-speed rear axle that helped the Ford Model T climb hills was the Ruckstell axle. It added an underdrive ratio behind the Model T’s standard planetary transmission, giving the car more pulling ability at lower speed.

The standard Model T transmission was famously simple, but its gearing could be limiting when the vehicle carried heavy loads or faced steep grades. The Ruckstell axle addressed that problem by incorporating planetary gearing into the rear axle. A floor-mounted lever allowed the driver to select the lower ratio when extra climbing or hauling ability was needed.

Ruckstell axles were especially associated with Model T trucks, though versions were also available for passenger cars. The lower gearing did not create extra engine power; instead, it traded road speed for increased torque at the wheels. That distinction explains why the device was useful on hills and with loads.

The Ruckstell axle was one of many aftermarket drivetrain improvements offered during the Model T era. Other firms sold auxiliary transmissions and overdrives, but Ruckstell became the best-known name associated with a two-speed rear axle for the Model T.