Manual Transmission System

In 1927, Warner Gear introduced a four-speed manual gearbox. The extra gear made high-speed cruising more comfortable due to less noise and vibration, increased fuel economy, and reduced engine wear. Oddly, the H-shaped gear pattern was opposite to today's pattern.

The manual transmission was, by the 1930s, a fairly mature and reliable technology. But the opportunity to improve on its operation took automakers into different directions. An unusual clutch spring was used in the Buick Series 40 for 1939. The cone-shaped spring was claimed to exert a high-pressure on the clutch plates to prevent slipping, while at the same time give a light clutch pedal feel for extended stop-and-go driving. It was an effective, but short-lived solution, doomed by durability problems.

Chrysler took an even more radical approach, with the adoption of its "fluid drive." Although the vehicle had a clutch pedal, it operated two vaned plates that transmitted power through shearing action in low-viscosity mineral oil. The design allowed drivers to stop without using the clutch, even leaving the gear selector in high. Providing quick acceleration was also not needed. Chrysler touted the design as being easier to drive, quieter, smoother, less prone to stalling and safer. Yet fluid drive flopped.

Traditionally, the transmission was placed directly behind the engine. It delivered the engine power to a drive shaft that powers the rear axle, a metal shaft to which one or more wheels were attached.

The simplest manual transmission, used in some cars, especially the smaller ones, is the sliding-spur gear type with three or more forward speeds and reverse. The desired gear ratio is selected by manipulating a shift lever that slides a spur gear into the proper position to engage the various gears. Early devices of this type required considerable skill on the part of the operator to shift the gears smoothly and without clashing the teeth.

Ease of shifting was improved by the use of synchronizing clutches that caused the two portions of a positive clutch to turn in unison before the driving and driven gear teeth touched each other during engagement. The only difficulty remaining in the operation of the sliding-gear transmission was the need for simultaneously operating the accelerator pedal, the clutch pedal, and the gearshift lever. The automatic transmission was developed to eliminate this manipulation.