As with the 365 variant, the model number referred to the swept volume of a single cylinder, whilst the new engine had the same 81mm bore of its predecessor, the stroke was increased to 78mm to give a total capacity of 4823cc. The engine of cars with the automatic gearbox had a factory type reference F 101 C 080.
Two banks of three Weber side draught twin choke 38 DCOE 110-111 carburettors were fitted, with twin coil and rear of engine mounted distributors, to produce a claimed 340bhp.
The Borg Warner three speed plus reverse automatic gearbox was, perhaps surprisingly for purists, an immediate hit with Ferrari clients, and would account for approximately two thirds of the cars manufactured for the remainder of the 400 into the 412 series production run. In Great Britain the figures were even higher, with the vast majority of purchasers favouring automatic transmission.
The power was transmitted from the automatic gearbox through a propeller shaft to a limited slip differential, and from there via half shafts to the independently suspended rear wheels with hydraulic self levelling units.

Although the chassis of the 400 series cars was structurally virtually identical to the preceding 365 GT4 2+2 models, there were nominal differences, which resulted in a new factory reference number F 101 CL 180 for this automatic transmission version.
Visually 400 series models can be differentiated from their predecessor by a small body colour spoiler on the lower edge of the nose, five bolt fixing for the five spoke alloy wheels instead of the single triple eared spinner, paired circular rear light assemblies, and the disappearance of the “Cavallino Rampante” from the radiator grille.

Inside the seat upholstery was made more sumptuous, and the stitch style and pattern altered, along with minor changes to switchgear on the centre console, and a change of style for the door release catch. The 400 Automatic continued in production until November 1979, during which time 355 examples were produced in the chassis number range19353 to 28261.
As with the 365 GT4 2+2, they were built and fully trimmed at the Pininfarina works in Turin, and then shipped to the Ferrari factory in Maranello for the installation of the mechanical components.
Right or left hand drive steering, with power assistance as standard, was available, but as with the other twelve cylinder models of the period, no USA market version was made.