Each carriage contains a separate diesel powertrain driving both axles on one bogie via cardan shafts.
Each powertrain consists of a 560 kW (750 hp) Cummins QSK19 engine driving a Voith T 312 bre three-speed hydrodynamic transmission which drives two axles in one bogie via a Voith SK-485 final drive.
The engine and torque converter were frame mounted underfloor and suspended from the car body by flexible mounts.
A third underfloor module contains cooling systems and an electrical generator.
The hydraulic converter includes an integrated retarder (brake).
Cooling fans and the electrical generator are powered via a hydrostatic drive.
The electrical generator provides a 400 V 50 Hz three phase electrical supply for the train, which is transformed or rectified to a 230 V 50 Hz single phase supply, a 110 V DC auxiliary supply, and a 24 V DC battery supply.
Connections bridge the main 400 V AC and 110 V DC supplies across the cars of each train set.
Component suppliers included Dellner (couplings), ZF (dampers), SKF (bearings), Westinghouse Brakes (braking systems).

The bogies are versions of Siemens' SF5000 bogie.
The design has an axle distance of 2.600 m (8 ft 6.4 in), with radial arm primary suspension utilising steel coil springs with rubber elements; the secondary suspension is an air spring design supporting a bolster.
Motor bogies have traction forces transmitted from bogie to frame via rods from a centre pivot.
Mechanical brakes are wheel mounted discs.
The Class 185 is heavier and has a stiffer suspension than the Class 158 it replaced on some routes; On some routes including the Hope Valley route, York to Scarborough Line, Hull to Selby Line (Micklefield junction-Hull), and between Northallerton and Middlesbrough the Class 185 units were not permitted to operate at the same speeds as the Sprinter type DMUs; however the higher acceleration of the Class 185 units could be used to partially offset the lower speed restriction.
Between Northallerton and Middlesbrough, Class 185s and Sprinters now use the same speed limits.

As delivered each train consisted of three cars; one end car (DMOSB) had 64 standard class seats in [2+2] arrangement with a mixture of facing seats with tables and airline style arrangements, as well as luggage and bicycle facilities; the middle car (MOSL) had 72 standard class seats also in a mixture of arrangements in [2+2] formation, and incorporated a standard toilet; the other end car (DMOCLW) had a further 18 standard class seats, and 15 [2+1] arrangement first class seats, plus a wheelchair space, and a reduced mobility access toilet.
Toilets were supplied by Driessen, seats by Grammer and Fainsa, and air conditioning from Air International Transit.
Each carriage contains a separate diesel powertrain driving both axles on one bogie via cardan shafts. Each powertrain consists of a 560 kW (750 hp) Cummins QSK19 engine driving a Voith T 312 bre three-speed hydrodynamic transmission which drives two axles in one bogie via a Voith SK-485 final drive. The engine and torque converter were frame mounted underfloor and suspended from the car body by flexible mounts. A third underfloor module contains cooling systems and an electrical generator. The hydraulic converter includes an integrated retarder (brake). Cooling fans and the electrical generator are powered via a hydrostatic drive. The electrical generator provides a 400 V 50 Hz three phase electrical supply for the train, which is transformed or rectified to a 230 V 50 Hz single phase supply, a 110 V DC auxiliary supply, and a 24 V DC battery supply. Connections bridge the main 400 V AC and 110 V DC supplies across the cars of each train set. Component suppliers included Dellner (couplings), ZF (dampers), SKF (bearings), Westinghouse Brakes (braking systems).
The bogies are versions of Siemens' SF5000 bogie. The design has an axle distance of 2.600 m (8 ft 6.4 in), with radial arm primary suspension utilising steel coil springs with rubber elements; the secondary suspension is an air spring design supporting a bolster. Motor bogies have traction forces transmitted from bogie to frame via rods from a centre pivot. Mechanical brakes are wheel mounted discs. The Class 185 is heavier and has a stiffer suspension than the Class 158 it replaced on some routes; On some routes including the Hope Valley route, York to Scarborough Line, Hull to Selby Line (Micklefield junction-Hull), and between Northallerton and Middlesbrough the Class 185 units were not permitted to operate at the same speeds as the Sprinter type DMUs; however the higher acceleration of the Class 185 units could be used to partially offset the lower speed restriction. Between Northallerton and Middlesbrough, Class 185s and Sprinters now use the same speed limits.
As delivered each train consisted of three cars; one end car (DMOSB) had 64 standard class seats in [2+2] arrangement with a mixture of facing seats with tables and airline style arrangements, as well as luggage and bicycle facilities; the middle car (MOSL) had 72 standard class seats also in a mixture of arrangements in [2+2] formation, and incorporated a standard toilet; the other end car (DMOCLW) had a further 18 standard class seats, and 15 [2+1] arrangement first class seats, plus a wheelchair space, and a reduced mobility access toilet. Toilets were supplied by Driessen, seats by Grammer and Fainsa, and air conditioning from Air International Transit.
British Rail Class 185