The E.636 was the first Italian locomotive adopting the Bo-Bo-Bo configuration with chassis divided into two articulated parts pivoting on the central bogie, which is very well suited for the often tortuous lines of Italy and that would have been later repeated on the E.645/646 and E.656 classes. The presence of a great number of wheels was considered important due to the presence of a number of high-slope lines in the Italian railroad network as it increases the adhesion limit, meaning that the locomotive is less prone to wheel slips. The new engines weighted approximately . Engines were initially the same as E.626. The 32R used a 3 kV catenary but this was soon shown to be inadequate and so were updated and provided with a new hollow axle transmission system. Mainly two different gear ratios were installed: 21/65 for sloping lines or heavy freight trains (maximum speed of , elevated later to 110 km/h), and the longer 28/65, with a maximum speed of , suited for passenger services.