As an 8-axle heavy load freight locomotive, SS4B was successfully developed by Zhuzhou Electric Locomotive Works in 1995 on the base of SS series locomotive. Till now, 49 sets of this type have been produced for Shenhua group for coal train traction.

SS4B locomotive is composed of two identical units of 4-axle locomotive by internal coupling, with each unit having a complete system and a driver's cab. A middle corridor is employed at the double-head position for entry from one unit to the other. The locomotive also has the function of being multiple operated externally and driver can operate the two units in one cab.

The carbody is integral supported and welded together with high strength low alloy steel.

Design speed of bogie reaches 100km/h and transmission system adopts central low inclined pull rod push-pull traction gear, which realizes higher coefficient of adhesion.

A traction transformer and two current rectifiers are installed on SS3B. Each rectifier energizes three shunt-wound DC traction motors, which can be isolated individually in case of failure to ensure normal performance of other motors so as to enhance utilization of locomotive.

Regarding its air brake, DK-1 E-P brake for SS series locomotives is adopted while backup resistance braking is employed for its dynamic brake..

Locomotive control system resorts to microcomputer control, which can realize data transmission, display and storage in locomotive for convenience of failure finding and disposal. With phase voltage regulating and step field weakening, constant current and quasi-constant speed characteristics control are achieved.

Layout in driver's cab conforms to UIC617－5.