Ford Model AA is a truck from Ford. As the Model T and TT became obsolete and needed to be replaced, Henry Ford began initial designs on the Model A and Model AA in 1926. Basic chassis layout was done rapidly and mechanical development was moved forward quickly. Body design and style was developed and then outsourced to various body manufacturers, including Briggs and Murray. The designs of the Model A shared parts and materials with the Model AA Ford, notably the body, engine and interior. The AA usually received plainer interiors than their car counterparts. The Model AA followed similar design changes to the Model A during the AA's four years in production, often delayed anywhere from three to nine months. The mechanical changes and upgrades were done during production of the vehicles. Body changes that occurred between 1929 and 1930 were also integrated into AA production, but leftover parts were used longer in the heavy commercial trucks.
Mechanical details
The Model AA Ford is powered by the same 201-cubic-inch (3.3 L) I4 engine that the Model A Ford used. The engine produced a maximum of 40 horsepower at 2,200 rpm. The engine featured an up-draft carburetor, six-volt generator, 2 and 4-blade fan, mechanical water pump, mechanical oil pump, electric starter and four-row radiator. All of these features were identical to the Model A Ford except the radiator. The engine could also be crank started if necessary by a hand crank that is inserted through a hole in the radiator shell. The Model AA was based on a chassis that was similar in design to the Model A Ford, except it was substantially larger and heavier to accommodate the work this truck was designed for.
Model AA Ford has a four-speed manual gearbox. The additional gear in the transmission is a "granny" or "creeper" first gear with a higher reduction ratio than the first gear on a Model A Ford to provide more torque to move a loaded truck. The second through fourth gears on the Model AA transmission were similar ratios to the first through third gears on the Model A transmission. The Model AA transmission also featured a lock-out on the shift knob for reverse that required a lever to be activated with the thumb so reverse could be engaged. This was done to prevent accidental engagement of reverse while the truck was in motion. Early trucks had a worm gear rear-end that limited the top speed of the truck. That rear-end was replaced by a ring and pinion differential to improve the speed of the truck. The later differential came with high speed and low speed options. Later models were fitted with braces on the outer casing of the rear-end to provide additional support to the rear-end housing.
The suspension of the AA Truck was similar to the Model A Ford in the front end. A leaf spring is centered in the front ‘A’ frame over the front axle. Shock absorbers were available for the front end. The rear suspension differed from the Model A Ford. The AA had leaf springs mounted to the chassis and shackled to the rear axle. The rear suspension did not have shocks.