Diesel locomotive break down. Hydraulic transmission for locomotives was developed in Germany. There is still debate over the relative merits of hydraulic vs. electrical transmission systems: advantages claimed for hydraulic systems include lower weight, high reliability, and lower capital cost. By the 21st century, for diesel locomotive traction worldwide the majority of countries used diesel–electric designs, with diesel hydraulic designs not found in use outside Germany and Japan, and some neighbouring states, where it is used in designs for freight work. In Germany and Finland, diesel–hydraulic systems have achieved high reliability in operation. In the UK the diesel–hydraulic principle gained a poor
TU7 diesel locomotive TU7 diesel locomotive TU7 (ТУ7) - Soviet, later Russian diesel locomotive for gauge – . The TU7 () was developed in 1971-1972 at the Kambarka Engineering Works to replace the aging locomotive classes TU4 () and TU2 (ТУ2). There were 3,361 locomotives constructed, of which several hundred were exported to the countries of the socialist community and affiliated countries. The TU7 - TU7A () was designed to be used on any gauge from to . In 1986 the locomotive design was updated and designated type TU7A (). The D4H and 9 locomotives D4Hr for standard gauge , also known as