Ural-4320

From the petrol Ural-375D to a diesel 6×6

The Ural-4320 exists because its predecessor drank too much petrol. UralAZ built the petrol Ural-375 from the start of the 1960s with a 7.0-litre ZIL-375 petrol V8. A diesel was the obvious answer, but the plant's own Ural-640 diesel, developed in the 1960s, was dropped for lack of production capacity.

The solution came from outside. In 1969 an engine designated YaMZ-7E641 and a matching gearbox were fitted to a Ural-375D, and from January 1970 this test truck covered nearly 20,000 km (12,400 mi). By 1972 the revised engine, now called YaMZ-740, was running in a prototype known as the Ural-E4320. Acceptance tests ended in 1975, and series production was approved on 31 December 1975.

The engine went into production at the KamAZ engine plant in 1976 as the KamAZ-740, and supply was tight at first. The first five series trucks were completed in December 1977, only 25 were built that year and output in 1978 reached just 100. Until about 1986 the trucks used the same load bodies as the Ural-375. The wider story of the factory is covered in the history of the Ural plant.

Production timeline

Chassis, cab and all-wheel-drive layout

The Ural-4320 drives all six wheels all the time, through a two-speed transfer case with a lockable centre differential. Torque is split one part to the front axle and two parts to the rear bogie. The axles use double-reduction final drives without their own locks, with an overall ratio of 7.32:1.

The frame is a riveted ladder design. Solid axles sit on leaf springs, and the two rear axles share a balancing bogie. 14.00-20 tyres are fitted all round, connected to a central tyre inflation system. Pressure can be set between 0.5 and 3.1 bar (7–45 psi): low for sand, snow or mud, high for paved roads.

The standard cab is an all-metal two-door unit for three people, and a four-door crew cab and a sleeper cab were offered. The load body seats 27 troops. Unlike the 12 V Ural-375D, the 4320 has a 24 V electrical system with two 12 V 190 Ah batteries. A rear winch with 65 m (213 ft) of rope and a pull of 70 kN can draw up to 40 percent of engine power through the power take-off.

Engines and gearbox: KamAZ, then YaMZ

The original Ural-4320 engine is the KamAZ-740.10, a 10.85-litre (662 cu in) 90-degree V8 diesel with direct injection, liquid cooling and a bore and stroke of 120 × 120 mm (4.72 × 4.72 in). It produces 156 kW (210 PS) at 2,600 rpm. Published torque figures differ, so none is quoted here.

The gearbox is a five-speed manual with an unsynchronised first gear, driven through a twin-plate dry clutch. Combined with the two-speed transfer case, it gives the driver ten forward ratios. The road and off-road transfer ratios are 1.3:1 and 2.15:1.

Why the engine supplier changed

KamAZ was the sole engine supplier at first. After a fire at the KamAZ engine plant in 1993, UralAZ built the short-lived Ural-43205 with its own Ural-744 engine and moved the main range to YaMZ diesels. The YaMZ-236 diesel is an 11.15-litre (680 cu in) V6, and the YaMZ-236M2 version produces 132 kW (180 PS). The YaMZ-238 is a 14.86-litre (907 cu in) V8; as the YaMZ-238M2 it is rated at 177 kW (240 PS). Turbocharged YaMZ engines followed in the 2000s.

In 2013 KamAZ stopped supplying engines altogether. Later trucks received a new generation of YaMZ six-cylinder diesels, starting at 169 kW (230 PS) and reaching 229 kW (312 PS) in a version paired with a ZF gearbox.

Diesel against petrol: the Ural-375D comparison

The reference figures show what the switch to diesel achieved. The Ural-375D's 7.0-litre (427 cu in) ZIL-375 petrol V8 produced 132 kW (180 PS) and typically used 45–50 L/100 km. The Ural-4320 has a reference consumption of 27–38 L/100 km (8.7–6.2 mpg US) on roads. Off-road work raises that figure sharply. With a 300-litre tank, the diesel truck covers about 700–1,100 km (435–684 mi), depending on conditions.

Ural-4320 specifications

The table covers the original KamAZ-740 version of 1977 to the mid-1980s. Where sources disagree, a range is given or the figure is left out.

Published width, height, ground clearance, gross weight and trailer load vary too much between sources to quote a single value. The payload range reflects the same problem: German references list the original truck at 5,000 kg, while English-language sources give 6,000 kg for V8 versions and 5,000 kg for the V6.

Variants and derivatives

Over about 40 years the Ural-4320 family grew to more than 1,000 versions, so the table lists the main indices only.

The Ural-3255 truck-bus puts a passenger body on the 6×6 chassis. The Ural-43202 is the semi-trailer tractor on this chassis, and the Ural-44202 tractor unit has its own page. Close relatives with separate model numbers, such as the Ural-5557 built from 1984, are covered separately.

Ural-4320 against its contemporaries

The Ural-4320 belonged to a small group of Soviet 6×6 army trucks, between the petrol ZIL-131 and the larger-engined KrAZ-255.

The closest relative in engineering terms is the KamAZ-4310, which used the same KamAZ-740 engine, carried a similar 6,000 kg and arrived four years later. The ZIL-131 kept its petrol V8, while the KrAZ-255 was already a diesel, using the larger YaMZ-238 V8 that later appeared in the Ural-4320-30 series.

In service and legacy

The Ural-4320 became the standard heavy truck of the Soviet army and was supplied to Warsaw Pact armies. Exports also went to several African countries, Iraq and Afghanistan. The East German NVA first procured the type in 1983 and had about 970 Ural-4320 trucks in service on 3 October 1990, alongside a far larger fleet of the older Ural-375.

The chassis carried more than cargo bodies. From 1976 the BM-21 Grad multiple rocket launcher was mounted on the Ural-4320, replacing the Ural-375D as its carrier. Refuelling tankers such as the ATMZ-5.5 and other special bodies followed. The truck has also found a second career in Truck Trial events.

Production did not end with the Soviet Union. UralAZ kept updating the 4320 with new engines and cabs into the 2010s. A joint venture with Iveco, formed in 1994, shaped later Ural cabs rather than the original 4320. The named successor arrived in 2015 as the Ural-NEXT, while the 4320 stayed in the range. Other trucks from the same factory are listed under all Ural models.

Preservation and collecting

The Ural-4320 is now catalogued as a classic vehicle on a European classic-vehicle marketplace alongside the Ural-375D and Ural-5557, and ex-Soviet military trucks draw a growing number of military-vehicle collectors.

The first task is to identify the exact version, since engines, cabs and payload ratings changed over four decades. Useful checks:

• The index on the data plate and in the papers, which separates a KamAZ-engined truck from the 1977–1993 era from a YaMZ-engined one.
• The engine type, which should match the index, because KamAZ and YaMZ engines need different parts.
• The central tyre inflation lines, valves and seals at each wheel, which suffer on trucks that have stood for years.
• The transfer case and the centre differential lock, which should engage in both ranges.
• The 24 V electrical system and the winch.

Registration rules for former military trucks differ from country to country, so the import and registration path should be clear before purchase.