From Ford Wiki
Ford TT used as a bus in Skanör
The Ford Model TT Truck was rated at one ton. It was based on the Ford Model T, but with a heavier frame and rear Axle. It was often equipped with a 'ruckstell axle' or some other accessory Gearbox which allowed the truck to have an intermediate gear between low and high, which was useful for hill climbing. It was often sold as a Chassis with the buyer supplying the truck body as needed. Mass production with Ford produced bodies ran from 1925 to 1927, but production of the Ford TT had started with the first TT chassis being released in 1917.
It was very durable for that time, but really slow compared to more modern standards. With standard gearing, a speed of not more than 15 m.p.h. was recommended, and with special gearing, a speed of not more than 22 m.p.h. was recommended, according to Ford Dealers Data Book 1923. Standard worm gear ratio was 7.25:1, special gearing 5.17:1