The numbers 4701 to 4712 of the PO were 4-8-0 express locomotives rebuilt by Chapelon from Pacifics of the 4501 to 4600 range in 1932 and 1933. The reason for the rebuild was that trains of 650 to 700 tonnes had to be accelerated to 120 km/h. He had already rebuilt the Pacifics 3701 to 3721 which now had much more power. On the other side, the adhesive weight of the three driving axles was still too small for heavy trains. So Chapelon decided to exchange the trailing axle against a fourth driving axle, what did not present many problems since the firebox was still narrow and deep.

Compared to the 3701 series, the steam lines were again enlarged and boiler pressure was increased from 17 to 20 bars. Like their predecessors, the 4-8-0 still had Nicholson thermic syphons and a double Kylchap exhaust. The valve gear was of the Lentz-Dabeg type and the diameter of the high pressure cylinders had been increased by 20 mm. These changes resulted in an output of 4,200 hp, with more than 3,000 hp available behind the tender. Although designed for 140 km/h, some problems with bogie centering and comfort in the cab were reported while running at the approved speed of 120 km/h.

In the following years, also the Nord, the État and the Est borrowed locomotives from this series for test service. However, no further locomotives of this design were ordered, but the SNCF ordered 25 of the similar 240 P in 1940. The older 4-8-0 locomotives had become 240-701 to 240-712 when the PO merged with the Midi in 1934. The SNCF designated them 4-240 A. Even later in their career, they still used the small three-axle tenders with eight tonnes of coal and 26 m³ of water due to many short turntables. The lines where they operated were electrified from 1943. Even though the northern and western divisions asked if they could used these locomotives, they were scrapped in 1952, like the 240 P.