Only minor modifications to the well-established 3.5-ton Mercedes-Benz L 3500 were made to increase its payload to 4.5 tons from March 1953, and turn what had accordingly become the L 4500 medium-duty truck into the best-seller among the short-nose truck models from Mannheim. Precisely 73,033 units of the new 4.5-tonner – which was soon redesignated the L 312 – were sold during its production time from 1953 to 1961, exceeding the sales total for the closely related evergreen, the L 311 (previously the L 3500 and L 3250) produced from 1949 to 1961 by approx. 18,000 units.
Higher payload in great demand
The 4.5-tonner introduced in 1953 responded to the customer demand for a higher payload. This was easily discernible in view of the increasing and notorious tendency at the time to overload 3.5-tonners. While the authorities tried to counter this worrying trend by imposing heavy penalties, Daimler-Benz responded by increasing the payload.
Neither was this particularly difficult in the case of the robust L 3250 base vehicle. It proved sufficient to fit the truck with slightly larger tires with a higher load-carrying capacity, strengthen the frame and rivet its cross-members. The entire chassis layout was such that despite various frame reinforcements, there was even a gain in flexibility. Telescopic shock absorbers at the front also did their bit to improve roadholding.
Making the best of the available possibilities
Although Daimler-Benz had modified both the transmission and the rear axle in keeping with the new weight conditions, there were critical observers who were not happy to accept that the new L 4500 was an autonomous, new model: "In the strict sense the 4.5-ton Mercedes cannot be seen as a new vehicle model at all, but merely as a further development," as a tester wrote at the time. Nonetheless he was also aware of the positive aspects of this approach: "There can be no objection to this," he continued, "for seldom has a truck model proved its worth so well and been produced in such large numbers as the 3.5-tonner."
A clever increase in pulling power
Daimler-Benz made absolutely no changes to the highly successful OM 312 engine also used in the L 3250 and L 3500, which initially generated 90 hp (66 kW) from a displacement of 4.6 liters and 100 hp (74 kW) from 1956. To ensure that the pulling power and climbing ability would not be inferior to that of the lighter 3.5-tonner with the same engine, the Mercedes engineers resorted to a clever ruse: instead of the 5.72 rear axle ratio normal for the L 3500 they opted for an almost 20 percent lower ratio of 6.83 in the 4.5-tonner, thereby elegantly compensating for the approx. ten percent higher gross vehicle weight (7800 rather than 7100 kilograms) of the L 4500.
In terms of the achievable top speed this meant that at 73 km/h the L 4500 was approx. 10 km/h slower than the L 3500, however good pulling power and the option of 1000 kg more payload was far more important to customers than a high top speed which could only seldom be exploited, at most on a level stretch of motorway. The assertion that a top speed "of 65 to 70 km/h is completely adequate" was also confirmed by a road test conducted in 1953, whose author rightly had no doubts about the great future of this concept: "Like its smaller brother, the new 4.5-ton Mercedes will make many friends," he accurately predicted as early as 1953.
The mainstay of production in South America
Whether as a platform truck with two wheelbase lengths, a dump truck (with optional four-wheel drive) or a semitrailer tractor, the L 4500 proved a runaway success, partly and not least because of its "conscientious lightweight design", as the plant described this combination of sound engineering and high payload in a brochure. It not only exceeded the total sales of its lighter colleague, the L 3500, but also served as a welcome ambassador for the overseas assembly operation in Brazil.
The first CKD kits already went to Brazil in 1954, where the L 4500 was an important factor in the commercial vehicle production of Mercedes-Benz do Brasil being developed at the time. From 1959 the L 312 was no longer only leaving the production lines in Brazil, but also in Argentina. More than 20,000 units of the L 312 were produced in South America. The even higher payload variant of the short-nosed trucks from Mannheim, the L 321 (with a 5.5-ton payload) introduced in 1957, only enjoyed a brief two-year production period in Europe, however it proved extraordinarily successful in South America where no less than 66,254 units were produced.