Manual steering gears predate the Model T era. The typical layout is a column and shaft leading from the steering wheel to a frame-mounted gear mechanism. This steering shaft rotates left and right, turning a cross-shaft within the gear. The cross-shaft rotates the pitman arm, and depending upon the front axle layout, the pitman arm moves either fore-and-aft or laterally.

The manual gear mechanism can be a worm-and-sector, worm-and-roller, cam-and-lever, or recirculating ball-and-nut design. In each type gear, the aim is to: 1) Change the direction of steering input motion by 90 degrees, and 2) Establish a steering ratio between the input shaft and the cross-shaft. Although mechanisms differ, the function remains the same: convert steering wheel input into pitman or steering arm rotation. Linkage connects the pitman arm to the steering arms and knuckles at the front wheels.

Types Of Manual Gears
In concept and basic design, manual steering gearboxes have changed very little in the past century. Prior to 1972, several American manufacturers produced manual steering gears. Despite similar outward features, these gears have different internal mechanisms. Let's discuss these components and steering gear terminology.

The worm/worm shaft/worm gear can be a spiral, screw-like gear or a spiral groove machined into the steering shaft. Some worms engage directly with the sector or roller teeth. On recirculating ball-and-nut gears, the worm is a machined, spiral groove in the steering shaft. The groove serves as a ball bearing race. In a cam-and-lever gear, the worm is a cam designed to move the pins of a lever shaft. When the steering wheel turns left or right, the worm or cam rotates clockwise or counterclockwise.

The sector, pitman shaft, cross-shaft, or lever shaft rotates the pitman arm. Though subtly different by design, each of these shaft types lay perpendicular to the centerline of the input or worm shaft. Supported by bearings or bushings, the shaft has splines and a nut at its outer end. The pitman arm attaches to these splines. Movement of the worm shaft rotates the sector/cross-shaft.

Various patents apply to manual steering gear designs. Manual steering gear terminology frequently associates a design with its manufacturer. These terms and names can be useful when describing or ordering parts for a manual steering gear.

Ross cam-and-lever steering uses a steering column tube or input shaft with a cam at the bottom. This worm cam resembles round bar stock with a spiral groove machined into the cam. A lever is at the inner end of the lever shaft. Pins on the lever engage the cam groove. At the outer end of the lever shaft, splines attach to the pitman arm. The lever pins move with the steering wheel and cam rotation, swinging the lever shaft and pitman arm clockwise or counterclockwise.

Ross cam-and-lever gears are common to Jeep, International-Harvester, and Studebaker trucks. The heyday of Ross gears was the pre-war period to mid-'60s. Primitive and wear-prone, light-duty Ross cam-and-lever gears have fixed lever pins and a higher friction factor than other designs. Heavier-duty Ross gears mount the lever pins on bearings. Those designs are available in both single- and twin-stud versions.

Gemmer worm-and-roller gears were popularized in '37-up Ford cars and truck models. The predecessor of the worm-and-roller was Gemmer's worm-and-sector gear. Vintage Dodge pickups also use this gear type. The roller rides on needle bearings and mounts on a shaft at the head of the sector. This rotating roller engages the worm. Friction is much less than with a worm and fixed-tooth sector; a fixed tooth design is sliding friction. The roller is a much smoother rolling friction.