Originally from Moscow
Evgeny Kochnev's book "Automobiles of the Soviet Army 1946-1991" provides an idea about the influence of the American REO M34 trucks on the design of the domestic ZIL-131. Even if this is so, then the Soviet Union chose a good option to follow. Work on the American car ended in 1949, and a couple of years later the truck went to the troops. The four-wheel drive three-axle M34, along with numerous modifications, became one of the most common vehicles of the US Army and received the nickname Eager Beaver, or "Conscientious" for its unsurpassed reliability. The appearance of the truck was not distinguished by elegance (as, indeed, of all American wheeled vehicles), the cabin was generally open, but the gearbox had 5 steps with synchronizers, and the overhead valve 6-cylinder engine developed quite decent 127 hp. with. The carrying capacity of the M34 on unpaved roads did not exceed 2.5 tons, and the hard surface under the wheels made it possible to load up to 4.5 tons.
In the USSR, the immediate predecessor of the 131st machine can be considered not the most successful ZIS-151, which, in turn, traces its history from the Lend-Lease Studebaker. In addition to a weak engine and a large mass, an important drawback of the truck was the dual-tire rear axles. On the one hand, this was demanded by the military in pursuit of greater carrying capacity, and on the other hand, it seriously limited the vehicle's passability on soft soils and virgin snow. When the legendary ZIL-157 appeared in the army, claims also appeared against it in terms of low carrying capacity and weak traction capabilities - it was not suitable for the role of an artillery tractor. It was for the artillery units in the mid-50s that they began to develop the ZIS-128, which, by the way, had many things in common with the previously mentioned "American" M34.
In the initial version, the car was called ZIS-E128V, but with the first prototypes, they stopped at the ZIS-128. This car was actually not a continuation of the ZIS-151 line, it was distinguished by a new transfer case, gearbox, centralized tire inflation system and other details. The cargo platform was lowered down in order to lower the center of gravity and simplify the unloading / loading of ammunition. History has not preserved for us a single copy of that experimental car, but the photographs show the trucks with at least three cabins, of which only one is all-metal. It is worth remembering that the experienced ZIS-128 appeared almost simultaneously with the first "classic" ZIL-157 vehicles. Such paradoxes of design work within one plant were explained by the requirements and captiousness of the main customer in the person of the Ministry of Defense. There was also another analogue of the future 131st machine - ZIL-165, which was a prefabricated hodgepodge of various units, in particular, the cabin was from the 130th. According to one version, it was the cramped cabin, as well as the weak in-line 6-cylinder engine, that caused the military to abandon this design in 1957. Then everyone already realized that the new car required a new engine with a capacity of one and a half hundred horsepower. And he was not.
Due to the motor hunger in 1958, the military turned up the prototype ZIL-131L (not to be confused with the later ZIL-131L timber carrier) with an experimental V-shaped 6-cylinder engine with a capacity of 135 hp. with. The vehicle featured a steel cargo platform with low sides and tapered rims.
First prototypes with index 131
The first ZIL-131 machines appeared at the end of 1956 and at first were equipped with 6-cylinder engines, which were later replaced by V-shaped "eights". It was supposed to develop the machine in two versions - ZIL-131 for artillery and ZIL-131A for the transport needs of mainly motorized rifle troops.
In fact, the ZIL-131 was not originally planned for widespread use in the ground forces - it was preparing a career for a predominantly artillery tractor. In the army at that time there was a ZIL-157 "Cleaver", which, according to most parameters, suited the military. That is, the 131st machine was not supposed to replace any equipment, but was originally an independent niche development. Perhaps that is why there was no particular urgency with the adoption of the machine. ZIL-157, by the way, was assembled until 1991, however, to a greater extent not for the army. But the mores and strategies of the Ministry of Defense of the Soviet Union at that time were notable for variability, and as a result, the ZIL-131 from an artillery tractor turned into a multipurpose truck.
History will show that in terms of the number of possible use cases, the three-axle all-terrain vehicle from Moscow will be perhaps the most demanded in the Soviet Army. In total, at the end of the 50s, six experimental vehicles were built, among which were transport, traction samples and even one truck tractor. After preliminary tests, by 1960, the factory workers presented seriously modified trucks to the military. In comparison with the Kolun, the ZIL-131 was more economical, took more cargo, but was somewhat inferior in cross-country ability. In the edition of "Autolegend of the USSR" it is also mentioned that the military allocated an excessive mass of prototypes, insufficient ground clearance and low fordication - no more than 1.2 meters with the required one and a half meters. At ZIL, the shortcomings were corrected by July 1960, but repeated tests revealed a tendency to skid due to an unsuccessful tread pattern and unsatisfactory operation of the interwheel self-locking differentials. After eliminating these shortcomings and modernizing the shielded electrical equipment, military specialists left for further work the only option for a future truck in a transport version. It was decided to abandon the artillery tractor.
The described prototypes of the ZIL-131 were already difficult to distinguish from future production models. There were branded angular fenders, a protective grille for the headlights and a wooden lattice body. The transmission was distinguished by relative lightness and simplicity, had an average through bridge, which favorably distinguished it from the similar design of the ZIL-157, in which there were as many as five cardan shafts. In addition, the cabin of the 131st ZIL was more spacious, and the pressure in the wheels was regulated by a system with an internal air supply. Having a high unification with the civilian ZIL-130, the army truck was distinguished by a panoramic windshield, which was a kind of nonsense for military equipment. Difficulties arose both with the replacement of the broken triplex and with the transportation of the curved glass. It is surprising that, subjecting the car to lengthy and captious tests, military experts realized too late the impracticality of curved panoramic glass from the ZIL-130. On January 19, 1959, engineer-colonel G. A. glare on the glass from the headlights of oncoming cars. The panoramic glass was not abandoned, but only divided into two parts.