From a 1984 article from the Light Commercial Vehicle Association magazine (which later became "This Old Truck" magazine and is now called "Vintage Truck" magazine:
"In 1948 Chevrolet was the first of the volume manufactures to offer a 4-speed synchro-mesh, helical gear transmission as regular equipment. It was an extra cost option. As a result of this complete redesign, the 4-speed transmission case was wider, higher, and longer. It was still of the same rigid, box-like cast iron construction as before. So that the new 4-speed transmission could be mounted interchangeably with the 3-speed transmission it was necessary to increase the length of the 3-speed transmission case and main shaft. Minor changes were made to the dash and tow panels in that a new seal was added to accommodate the steering column, gearshift, and the transmission cases. The new foot operated parking brake was moved to the extreme left side of the cab. A hand release rod was located just below the instrument panel. The foot operated parking brake offered a couple of advantages, it was easier to apply because more pressure can be applied with the leg and it helped to provide smooth starts on hill by allowing the driver to simultaneously accelerate the engine, engage the clutch, and release the parking brake lever. Only a slight amount of effort was needed to release the parking brake because of an 8 to 1 mechanical advantage. A new left-hand inner fender skirt was provided to allow space for the pedal mounting lever."
