Long overdue
During the acceptance of the Ural-375N carburetor, the state commission pointed out the main drawback of the truck - the absence of a diesel engine in the engine range. Older KrAZ vehicles from the very birth possessed a low-speed, but still a diesel engine YaMZ-238, and the Miass all-wheel drive remained gasoline-powered. Meanwhile, theoretical calculations showed that a diesel engine with a capacity of 200 liters. with. will be 37-50% more economical than the carburetor one, raise the average speed by 10-17% and provide an annual operating saving of 500 rubles. All this at a higher cost of producing a diesel car - an average of 18-20%. In 1965, in Miass, they tried to install the latest Yaroslavl engine YaMZ-236 with a capacity of 180 hp on the Ural-375D. with., but the entire circulation of these diesel engines went to the Minsk Automobile Plant. There was no hope of expanding the motor production of this particular power unit in Yaroslavl, and for Ural they decided to adapt the promising YaMZ-641 diesel engine. It was an eight-cylinder V-shaped 160-horsepower engine, which did not differ in reliability and long service life. And most importantly, its power did not provide the necessary power supply of the truck, which was required by military customers. As a result, Miass began to develop its own 210-horsepower Ural-640 (V-8) diesel engine with a working volume of 9, 14 liters.
All work on the power unit was closed in connection with the construction in Naberezhnye Chelny of a plant for the production of the famous KamAZ-740 engines (250 thousand per year), which do not differ in layout solutions from the Miass diesel prototype, only the working volume of the power unit was increased to 10, 85 liters. If you try on a new engine at the Ural, it turns out that the diesel is 19% less revolving than the carburetor ZIL-375, but 30 hp. with. more powerful and its torque is 14% higher. The motor turned out to be immediately 240 kilograms heavier than its predecessor, which changed the weight distribution of the army truck. The development of the engine was carried out in Yaroslavl, the first prototypes were called YaMZ-740 and they developed power in the range of 180-210 liters. with. Due to the complexity of the project, at the Yaroslavl Motor Plant, the development of engines for future three-axle KamAZ and "Ural" vehicles was carried out with the support of diesel specialists from NAMI.
In 1972, several trucks were built with promising engines: "Ural-4320" (onboard with a carrying capacity of 5.5 tons), "Ural-43201" (lightweight onboard with a platform without wheel arches with a carrying capacity of 5 tons), as well as two saddle the Ural-4420 and Ural-44201 tractor units. Some sources indicate that the first "Urals" with diesel engines from Yaroslavl received the index 34320. Such "Urals" passed during test runs of 60-100 thousand kilometers in the South Urals and the north of the Tyumen region. At the same time, onboard vehicles were dragging massive 7-ton MAZ-5243 trailers, which were not intended for Miass trucks. The tests showed the reliability and high service life of the Yaroslavl motors, but at the same time the need to modernize some of the Uralov units and assemblies was revealed.
The engine, in comparison with the carburetor one, became less responsive, but more powerful, and this required a change in the gear ratio of the main gear from 8, 90 to 7, 32. In another case, it could not withstand increased loads. The large weight of the engine required the restructuring of the frame (a cross member appeared in front), the front suspension and the installation of new 254G-508 wheels with toroidal landing shelves. Also, based on the results of the tests, the grip was strengthened and the transfer case was modified. The new engine was not only heavier, but also larger than the carburetor predecessor, which required a redesign of the radiator grille. As mentioned above, the heavy engine changed the distribution of the machine's weight - now the front axle accounted for 32.5%, and the rear bogie 67.5%. "Ural-375D" had an underloaded front axle, which accounted for only 29.3%. All this, coupled with the increased power, improved the cross-country ability of the diesel "Ural" on soft soils.
Western patterns
The new diesel engine YaMZ-KamAZ-740 was good for everyone: powerful, economical, its resource went off scale for 170 thousand kilometers, but it was chronically not enough for Miass trucks. Since 1977, the Ural plant has been on the sidelines in front of the growing main consumer of engines KamAZ. It was at this moment in the history of diesel "Urals" that a radical change could occur, consisting in the transition to air-cooled motors. This was largely facilitated by the country's leadership, fascinated by the "Bam" Magirus-Deutz with Klockner-Humbold-Deutz AG (KHD) engines. The results of the operation of Czech Tatra trucks, also equipped with air-cooled diesel engines, were also positively assessed. In the most severe frosts after the change, Magirus and Tatra did not require tedious draining of water from the cooling system, and they were also easier due to the lack of a radiator, pump, thermostat, pipes and hoses. It is worth making a historical digression and returning to 1970, when a test run of several Ural-375s with German Deutz F8L413 diesel engines with a capacity of 210 hp was organized in the Soviet Union. with.
In addition to "Uralov", air-cooled diesel engines were mounted on GAZ-66, ZIL-130 and 131, MAZ-500 and GAZ-53. Light trucks were powered by Deutz F6L912 engines. After analyzing the situation, it was decided to develop, together with West German specialists, two lines of air-cooled diesel engines - work on the younger family was entrusted to the Gorky Automobile Plant, and the older one to the Ural Automobile Plant. In the first case, the diesel engines were supposed to be installed on the GAZ-66, and in the second - on the family of modernized "Urals" under the code "Land", which will be discussed in the following materials of the cycle. Miass's problem was that the plant located in the city was not very large and was not ready to host a motor production. Therefore, it was decided to build in Kazakhstan an enterprise specializing exclusively in F8L413 diesel engines under the Ural-744 brand - the Kostanay Diesel Plant (KDZ). This plant took a very long time to build and only in 1992 produced the first motors, and two years later it went bankrupt, having managed to assemble only 405 motors. So "Ural" forever lost air-cooled diesel engines, which, however, should not be grieved - this technical direction of development is currently more marginal than widespread. And the Ural-744 motors were already technically and morally obsolete models by the mid-1980s.
Ural-4320
With all the external similarities, the diesel "Ural" has a lot of differences from the carburetor 375 model. A new "KAMAZ" gearbox appeared on the car, the 12-volt electrical equipment was replaced by a 24-volt one, and the interior of the cab was largely unified with the KamAZ-4310 family. Due to the increased traction capabilities, the Ural-4320 was now able to tow a trailer weighing 11.5 tons, and the maximum speed increased to 85 km / h. The first modification was the 4320-01, equipped with reinforced cardan shafts, steering and a cargo platform raised by 120 mm. Also in the factory production line was "Ural-43203" - a special chassis for mounting superstructures for various purposes and, of course, weapons. It was on this base that the Grad multiple launch rocket system was built, which has become one of the symbols of the Ural trucks.
I must say that in the 70-80s, up to 60% of all production of the automobile plant in Miass was taken by the Ministry of Defense. At the same time, not only the classic onboard Ural-4320 and chassis based on it went into the army, but also vehicles for the national economy. So, the 7-ton national economic "Ural-43202" with a wooden platform with the sides folding on three sides and devoid of a wheel pumping system was also purchased by the army for work on public roads.
There was also a demand for the Ural-4420 civilian truck tractor, which was adapted for towing 15-ton army semitrailers. Wide unification with the previous carburetor model allowed the army to simply rearrange the equipment on the new diesel "Urals". Among other things, trucks from Miass received sets of special railroad tracks that allow the car to move along the railroad bed. Such "Urals", which develop a traction force of 6, 5 tons on iron wheels, are used in shunting work, to supply track links for track layers, as well as in the transportation of personnel and cargo. Also, in a long list of options, you can single out a car with the index 432001-01, designed for the northern regions of the country.
Six years after the start of production, in 1983, Ural-4320 receives the State Quality Mark. And until 1985, the plant could not bring the production of diesel trucks on a par with the 375 series gasoline cars - the latter were invariably produced in large quantities. The reason for this was the chronic shortage of power units from Naberezhnye Chelny. In this situation, "Ural" could not dictate its own terms - there was no motor production of its own, and the construction of an enterprise in Kustanai was delayed. When KamAZ-740 engines began to be enough for everyone, the army even had an idea to re-equip all carburetor "Urals" with diesel engines. They even came up with a name for the new hybrid - "Ural-375DD". But in 1993, a major fire broke out at the engine plant in Naberezhnye Chelny, the supply of engines to Miass was interrupted and a new chapter opened in the history of Ural.
