As a stronger addition to the BB 63000, the BB 66000 was created with basically the same structure. The first 40 locomotives still bore the designation 040 DG and were re-designated in 1962, a total of 318 units were built. While the BB 63400 and BB 63500 got a V12 engine from SACM, the BB 66000 had a V16 from the same family with 1,400 hp. The first engines were delivered with a top speed of 105 km/h, but they were soon subsequently approved for 120 km/h and all others as well ex works.
From 1968, 106 BB 66400 were built, which were based on the latest BB 66000 series and were equipped for electric train heating. Already between 1960 and 1962 13 BB 66600 had been completed, which had a Pielstick engine. The first three of these were created by conversion and ten others were newly built. Between 1985 and 1991 a total of 34 BB 66000 were equipped with the same engine and designated BB 66700. They had a modified gear ratio for 80 km/h in order to increase traction and use it for shunting.
The locomotives were initially used in regular service with passenger and freight trains. Like the BB 63000, they were considered “jack of all trades”. The capabilities for multiple working were somewhat limited, since the sub-series were partly not compatible with each other. Over time, the engines were phased out of passenger service and were primarily only used for lighter freight trains.
In 2005, a total of 91 locomotives were fitted with new MTU 12V 4000 engines to extend their service life. In 2019, 64 of these were still in use, mainly in the SNCF freight and infrastructure areas. The BB 66600 with Pielstick engines had already been retired in 1997 and the last BB 66700 disappeared in 2018. At that time some of the unconverted locos with SACM engines were still assigned to the STF Infrarail.
