The locomotives are fitted with monomotorbogies with two different gear ratios. This allows them to increase their tractive effort in exchange for a reduction in their top speed. This makes them suitable for both freight and passenger trains. They acquired the nickname Danseuses (dancers) due to their tendency to sway from side to side at speed, which led to them being blacked at a number of depots.[5]
They were built in three distinct batches, leading to detail differences. They remain in use as mixed traffic locomotives, mostly with TER and but with some remaining for special duties. Thirty locomotives, dedicated to empty stock moves, have been reclassified as BB 88500.[2] Likewise in 2001, 20 of the class were rebuilt for freight banking workings on the Maurienne line. They were classified as BB 8700 for this period.