This loco is a 1Bo-Bo1 type version of ZDM3 locomotive, fitted with two addition pony trucks, one of each end, to reduce the axle load to it.

Fit for operating in 2ft 6in (762 mm) narrow-gauge sections of Indian railways with permissible axle load upto 7t.

Many components and sub-assemblies need on ZDM4A locomotive, specially in electrical, pneumatic, cooling water, air intake, fuel and lube oil systems, are common with those fitted on WDS4 and ZDM3 locomotives.

The transmission fitted on the locomotive is Voith make, L4R2U2 type, which is hydraulically reversible and is introduced first time on the Indian Railways.

The 2-axled bogie of the locomotive has two stage suspension arrangement - primary suspension is of coil-springs and secondary of megi-rubber spring. Hydraulic check absorbers are fitted across secondary suspension.

Wheel sets are attached to the bogie frame with leaf spring guide plates by means of serrated joints. These guide plates, being laterally stiff and vertically flexible maintain relative alignment of wheel sets with bogie frame and also transmit traction and braking force.

The pony truck shares the superstructure weight through a group of 4 coiled springs, placed in parallel between pony truck and underframe. The pony truck is free to glide underneath the frame, during its lateral displacement, while negotiating curves and turnouts. the sliding surface is provided with antifriction Tuflon liner.

The special devices to limit the max. tractive offout and prevent wheel slip are provided on the locomotive. The speed indicator-cum-recorder is Deuts make, electrical type.

Transmission --- Voith make, L4R2U2 type.

Axle Load --- 7 tonnes

Power output --- 700 hp

Bogie type --- 1Bo-Bo1 fabricated from steel plates to IS:2062.

Max speed --- 50 kmph