Due to inadequacies of the manually operated, mechanical transmission of the D-series DMUs and the required higher passenger capacity, new four-part multiple units were ordered from 1964. These were initially also given the series designation Д (D) and only after 98 units were manufactured were they re-designated Д1 (D1) to distinguish them.
Externally, the most noticeable difference was the second trailer on the new multiple units. If required, operation with three or four trailers or in multiple working was also possible. Each end car was powered by a diesel engine, which was a direct development of the engines from the older vehicles and, thanks to the added turbocharger and intercooler, produced 730 hp. The hydromechanical power transmission had three gears. While first gear transmitted power through a torque converter, the other two gears were mechanical. Since these gearboxes were now shifted automatically, this meant that the work of the driver was made easier. A total of 605 units were built up to 1988. New powered bogies were introduced during production, with the outer axle now being the carring axle rather than the middle one.
They were used on non-electrified suburban lines throughout the European part of Russia. In the earlier trainsets, technical problems in the drive train became apparent over time, so that the vehicles used in Russia got new hydraulic transmissions between 1995 and 2002 from the DMUs of the ДР1А (DR1A) series and new engines. Many vehicles remained in other countries after the collapse of the Soviet Union. In the Baltic States, they were already phased out shortly after the turn of the millennium. In Moldova, a comprehensive modernization of the interior and powertrain took place from 2012, during which the vehicles were given a modern, streamlined head shape.
