These are the newer class of dedicated mainline diesel passenger locomotives. Transfer of technology from GM's GT46PAC models.

The locos are rated at 4000hp and use 3-phase AC traction motors with maximum speed of 160 kmph

The fabricated underframe has a rigid design. The bogies are GM's light-weight cast HTSC bogies similar to those of WDG4 locos but meant for passenger use.

The suspension is a two-stage suspension. They have an interesting Bo1-1Bo wheel arrangement.

The bogies are said to have a 'million mile' overhaul interval because of a reduction in the number of wearing surfaces.And usually scheduled for a 90 days return for maintenance.

Recent WDG4 units have GTO control of the traction motors.

The EM2000 onboard microprocessor system provides a flexible and expandable control system with complete self-analysis and unit history features.

WDP4B are modified versions having 6 traction motors with individual inverters, Co-Co bogie type, axle load of 20.2t, Gear Ratio 17:77, 4500 hp and the maximum tractive effort is 384.4kN with wider cabs & 150 kmph of top speed. Prodcution started on 2010. Traction control uses IGBTs instead of GTOs. Can be used as HOG.

WDP4D refers to a dual cab version of the WDP4/WDP4B design, intended to eliminate the problem of running long hood forward. The Cab-I have a wider profile like WDP-4B, to improve visibility compare to Cab-II which is smaller.

WW PGR governor. Unit fuel injection, centrifugal pump as with WDP-2, cooling and fan as in WDP-2.

Transmission --- Electric with TA-17-CA6A alternator, 900rpm, 2200V AC/3000V DC, 1600A AC, 2100A DC.

Loco weight --- 119 tonnes

Bogie type --- Bo1-1Bo fabricated cast HTSC bogies.

Tractive effort --- 27 tonnes at 32% adhesion.