The original Y Type was a 3-ton 4x2 truck powered by a Daimler four-cylinder inline 5,700 cc petrol engine that developed 40 brake horsepower (30 kW) at 1,300 rpm, it drove the rear wheels through a four-speed gearbox, the wheels having solid rubber tyres.

[1][2] The Y Type had an open, canvas covered cab and a fixed side timber body, typical of military cargo vehicles of the period.

[1] The YA, introduced in 1917, replaced the Daimler engine with a Tylor four-cylinder inline 7,700 cc petrol engine that developed 49 brake horsepower (37 kW) at 1,300 rpm, the YB introduced a pressed steel frame whilst the YC used a David Brown Ltd. worm-gear final drive.

[1] Whilst AEC was founded in 1912, a sales agreement meant that all of its products were marketed by and branded Daimler, in June 1916 the company's factory, at Walthamstow, was placed under direct government control and the lorries were branded AEC from that date, although the Y Type's distinctive Daimler radiator was retained.

[1] as a 5-ton lorry[3] A number of Y Types were sold to civilian operators after the war, a common conversion saw the military body removed and the chassis used as the basis of an omnibus.