Development The Unimog 411 was not a completely new development, rather Daimler-Benz derived the 411 series from the predecessor 401 and 402 series. In the 1950s, the Unimog design department under the leadership of Heinrich Rößler took a wait-and-see approach to new developments, even though consideration was given to offering the Unimog 411 with a 40 hp (29.5 kW)
diesel engine and an 80 hp (59 kW) petrol engine. However, these ideas were only implemented in later model series. The developers' hopes were pinned in particular on the 411 with an all-steel cab. The most important focus of the development department was primarily on demonstrating, testing and improving the Unimog as such. The main changes to the 411 compared to its predecessor were an increase in engine output by 20%, reinforced shock absorbers, reinforced crossmembers for the engine, from 1959
plain bearings instead of
roller bearings for the manual gearbox and enlarged tires with the dimension 7.5-18″ In addition, the front end of the 411 was redesigned, with wider beading on the hood. The radiator grille was also made smaller; it was now a square grille painted in the vehicle color instead of the struts of its predecessor. With the Unimog 411, Daimler-Benz set itself the target of selling 4,000 vehicles a year. Nevertheless, the 411 was more of a small vehicle with an output of just 34 hp (25 kW) powerful diesel engine, which was considered too underpowered for some applications. Analysts at Daimler-Benz warned that the annual production rate of the Unimog 411 would fall below 3000 vehicles after 1960. This point was reached in 1964. Daimler-Benz therefore introduced a larger Unimog in 1963, the
406. The 411 was thus transformed from the former core product of the Unimog range into a light series. However, the further development of the Unimog 411 did not end there; from 1963, the axles of the
Unimog 406 were also fitted to the 411 in a modified form. These axles are more stable, cheaper and easier to maintain. From 1967, the 411 received the same bumper as the
Unimog 421. After the introduction of the type 411c in 1965, the 411 series was no longer developed further on a large scale; the models with an extra-long wheelbase were the last major innovation to be added to the Unimog model range for the export market from 1969. In March 1966, the Unimog 421, a technically similar vehicle with a much more modern appearance, was presented in the same segment. The 421, which had the technology of the Unimog 411 and a 2-liter pre-chamber engine of the type OM 621 with 40 hp (29.5 kW), was actually designed as an inexpensive addition to the 406 series, But from 1970 onwards, the Unimog 421 was already much more popular than the similar but older and weaker 411 and was preferred by customers. Dhe Unimog 411 continued to be built unchanged. Production was only discontinued in October 1974 after 39,581 vehicles. Presumably some vehicles were produced again in 1975 for a military customer.
Distribution On the West German market, the basic version of the Unimog 411 cost DM 12,500 as a convertible when it was launched in 1956. It initially had the OM 636.914 engine, which produced 30 DIN hp (22 kW) at 2550 rpm. As the Unimog 411 was too expensive for some customers, an "economy model" was offered from 1957 to 1959, the U 25. The U 25 was given the independent model number 411.116. It lacked the windscreen, side windows, windscreen wipers, soft top and other small parts, the seats and engine came from the Unimog 2010, and the transmission ratio of the
portal axle was also changed. It was a failure, only 54 units were sold. At the end of the 1950s, the 411 model series was also exported to the USA, where
Curtiss-Wright sold the 411.112 and 411.117 models; the Mercedes-Benz brand name was retained. In 1965, the basic version cost 15,300 DM. Daimler-Benz AG achieved the largest turnover with Unimog sales in West Germany. In 1962, worldwide sales of the U 411, excluding the spare parts business, amounted to 54,870,000 DM.
Prototype for the French army At the request of the French army Daimler-Benz built a prototype based on the 411 series with a
gasoline engine in 1957. The vehicle was given the chassis number 411.114 75 00939 and was assigned to type 411.114, which was reassigned to the extra-long wheelbase models in 1969. The
prototype 411.114 had the long wheelbase of 2120 mm, transmission and clutch of the
Unimog S and tires of dimension 7.5-18″. The desired and installed four-cylinder engine was the M 121 with a displacement of 1897 cm³ and an output of 65 hp (48 kW) at 4500 min-1 as well as a maximum torque of 128 N-m at 2200 min-1, as it was also used in the Mercedes 180. The top speed is 90 km/h. The reinforced windshield with the windshield wipers at the bottom is a distinctive feature. The French army tested the vehicle over a period of almost 9000 operating hours and decided not to procure it due to its high center of gravity. On the basis of this prototype, Daimler-Benz developed further military vehicles with a payload of one ton.
Westfalia cab Like the Unimog 401 and 402 before it, a closed cab was also offered for the Unimog 411, which was manufactured by Westfalia in Wiedenbrück. Daimler-Benz equipped the Unimogs with this cab ex works. When production of the 411 series began in August 1956, the type
B cab, which had already been built for the Unimog 401, was modified for the new Unimog 411 chassis and continued to be built almost unchanged on the outside. It has the model 411.520. This cab is nicknamed the ''frog's eye
and was only built 1107 times, the models 411.111 (1720 mm wheelbase) and 411.113 (2120 mm wheelbase) were equipped with it until they were discontinued in October 1961. Westfalia had already produced a new cab for the Unimog 411 in 1957. It has the model 411.521 and is designated as cab type DvF''.It was only built for the 411.117 and 411.120 models with 2120 mm wheelbase. DvF stands for Type D, widened cab. As the name suggests, its dimensions were significantly larger than those of the Type B, it has a 30% larger volume and is wider than the Unimog's loading platform. The windshield is undivided and the ergonomics have been significantly improved. The shape follows the truck design of the Mercedes-Benz brand in the 1950s and 1960s with an elliptical radiator grille with headlights framed on the outer edge and lavish chrome trim. Unlike the convertible models, the front bumper is more rounded and more strongly curved at the ends. On request, Daimler-Benz equipped the DvF cab with a heater. A disadvantage of the DvF cab was the high heat load caused by the engine exhaust heat. The reason for this is the engine cover, which protrudes far into the passenger compartment and does not sufficiently insulate the cab from the engine. Production of the Unimog 411 was discontinued in 1974, but Westfalia continued to build the DvF cab until 1978. In the mid-1960s, Westfalia also tested a
GRP hardtop for the convertible versions of the Unimog 411. It offered better protection from the weather and better visibility to the sides than the fabric top. Although brochures were printed and the hardtop was included in the official Unimog catalog, it was hardly ever sold. It is not known how many hardtops were produced.
Annual series change Prototype 411 1957 The 411 was extensively modified in 1957. The
indicators were removed and replaced by conventional car indicators. Other external innovations included the new Mercedes badge on the hood and the modified rear lights. The engine output was increased to 32 hp (23.5 kW) from March and the transmission
synchronized could be supplied on request, in July new springs with a wire diameter of 19.5 mm instead of 18 mm were fitted to the rear axles, and from September a reinforced steering system with a three-spoke steering wheel from Fulmina was installed. In the convertible models, the side windows made of
Cellon were replaced by
polyvinyl chloride windows as early as May 1957 . Mercedes-Benz also introduced the economy model U 25 in May.
1959 From January, the synchronized gearbox, which had previously only been offered as an optional extra, became standard equipment.
411a 1961 In October 1961, the Unimog 411 underwent a comprehensive model update, which upgraded the series, particularly in technical terms: the original type 411 was replaced by the type 411a. The 411a was launched on October 9, 1961. was produced in series and differs from the original 411 in its ladder frame with higher longitudinal members: 120 mm instead of 100. In addition, a newly introduced hydraulic system with front and rear power lift was offered and the cab was fitted with a three-point suspension, The type 411a can be recognized by the headlights, which are no longer attached to the frame but to the radiator grille, causing them to protrude slightly forwards, as does the front bumper, which is curved at the ends. The flatbed has four instead of three side boards on each side and is 30 mm away from the cab.
411b 1963–1964 In March, production of the 411a was discontinued due to the new 411b. The windshield was increased from 410 mm to 450 mm, and the convertible models were given a triangular window behind the A-pillar. At the rear, the fenders were completely black. Other technical changes included a modified exhaust system, a hydraulic
power steering system offered as an optional extra and a new, now two-stage master brake cylinder.
411c 1965 The 411b was built until February 1965, from February 1965 the type 411c was produced in series, the main difference to the 411b being the 2 hp (1471 W) increase in engine output. Daimler-Benz continued to install the OM 636.914 engine; however, the rated speed was increased from 2550 rpm to 2750 rpm. In addition, the
cylinder head,
injection pump and throttle body were modified. The rear hood mount, the
speedometer in the cab, the V-belt pulley for the compressor and the rear lights were also modified. With the introduction of the type 411c in 1965, there were three models - 411.118, 411.119 and 411.120 - and nine models.
1966 From April 1966, the standard color of the Unimog was changed from Unimog green (DB 6286) to truck green (DB 6277). The dropside hinges of the Unimog 421 were installed and the rear spring brackets were cast. The models with the Westfalia DvF cab were given a handle on the A-pillar to make it easier to get in.
1969 The last major innovation came in 1969, when the extra-long wheelbase of 2570 mm was introduced for export with the 411.114 model. The model 411.114 was primarily supplied to the Portuguese military, which used the vehicle in the civil war in Angola. Dhe fulminal steering was replaced by a ZF Gemmer steering of type
7340. In addition, the fuel lines were made of plastic. == Models ==