Early on, the Ingolstadt-based Two-Wheeled Vehicle Design department started designing a bubble car - however, they would never actually build the “Moppel,” as the project was called. The Passenger Car Development department picked up on the idea and designed a four-wheel, three-seater micro-car with central steering. The body was made out of innovative glass-fiber reinforced plastic. DKW dealers treated to a viewing of the tiny car were less than impressed, and the work on the STM II project was mothballed. The three-seater morphed into a four-seater with an air-cooled longitudinally mounted two-cylinder two-stroke engine, front-wheel drive, torsion bar-sprung axles and plastic body. The results of several crash tests with the car – now dubbed the STM III – and the departure of head of development Robert Eberan von Eberhorst prompted the Auto Union management board to shut down the plastic small car project completely in fall 1956. Over a period of five years, Auto Union had made no progress whatsoever in realizing its vision of a “small DKW” despite all its efforts.
Technical director Oskar Siebler, who had returned to the company along with Dr. William Werner, was now charged with developing a state-of-the-art compact car with sheet steel body in the shortest possible time using all the lessons learned from the plastic small car project. Auto Union caused a stir at the 1957 International Motor Show in Frankfurt with a prototype of its new small car, the “DKW 600.” The body followed the trapezoid line, but also drew on design features of the plastic small car. Particularly the rear wheel arches, the window line, the rear roof edge and the reinforcement beads on the hood and trunk lid shared many similarities with the STM III.
The DKW 600 was powered by a water-cooled two-cylinder two-stroke engine producing 30 hp at 4,200 rpm. The longitudinally mounted engine drove the front wheels via a four-speed transmission with freewheel clutch and internal drum brakes. The front and rear axles were torsion bar-sprung; two v-links provided wheel guidance at the front axle. The rear axle was a lightweight, slotted tubular axle guided by two rear wheel swing arms. The rear torsion bar was protected in the frame crossmember. In many respects, the prototype presented at the International Motor Show was not yet finished.
Following the takeover of Auto Union GmbH in March 1958, engineers from the new parent company Daimler-Benz AG worked on getting the small car ready for production. Due to manufacturing constraints, the body was simplified in many places and the engineers replaced the two-cylinder engine, which could not quite shake its poor reputation, with an all-new water-cooled three-cylinder two-stroke inline engine with loop scavenging. A 180 mm single-plate dry clutch from F&S and the optionally available Saxomat automatic clutch transmitted the power.
The main problem, however, was the lack of production capacity. The Düsseldorf plant was running to capacity with production of the various 3, 6 and 1,000 models; the Ingolstadt “smelting works” was not suitable for setting up rational high-volume production. In April 1958, the decision was finally taken to build a new automobile plant on a site outside downtown Ingolstadt. One of the reasons for this decision was the existing pool of trained staff on hand for new projects due to the decline in motorcycle and Schnelllaster truck production. The groundbreaking ceremony took place in July 1958 and 13 months later the first DKW Junior with a ZF transmission rolled off the production line.
In September 1959, two years after presenting the prototype, the DKW Junior took center stage at the Frankfurt International Motor Show. The most important change compared to the DKW 600 was the all-new 750 cc three-cylinder two-stroke engine. The turbine-like quiet engine produced 34 hp at 4,300 rpm and powered the front wheels via the ZF fully synchronized four-speed transmission 4DS6-3. There was no freewheel clutch; however, its absence made no difference thanks to the engine’s excellent smooth running. The brake drums were mounted internally on the transmission and also acted as a parking brake. The propshafts featured a universal joint with a spline end on the transmission side; constant velocity joints were fitted to the wheel side. This design tended to cause shaking under load, which could only be partly eliminated by applying various quantities of different lubricants to the spline end. Apart from that, there were no faults with the driveline and chassis of the Junior 750, which was given the internal designation DKW F 11/60. The car was extremely safe to handle, leading to genuine bursts of enthusiasm among testers. 118,986 units of the Junior 750 were produced between July 1959 and December 1962 - altogether, over 340,000 transmissions would roll off the production line at ZF over the next four years as part of the major order for the next-generation Junior de Luxe.
The equipment had become too spartan in some respects; numerous critics pointed in particular to the rubber loops to pull the doors shut, the absence of a fuel gauge, the hood without a lock and the awkwardly positioned shift lever. Some of these shortcomings were quickly remedied. By October 1959, for example, a fuel gauge had already been fitted instead of the single warning lamp; however, other problems simply could not be fixed.
The Junior went on sale with a factory-fitted Webasto sliding roof from March 1960; the Saxomat automatic clutch, familiar from the 1,000 model, was added in April 1960. In March 1960, the Junior received a visual facelift with chrome-plated window trim strips. At the same time the interior was upgraded with a newly designed dashboard with radio console and the doors now came with armrests. This first series of the Junior 750 was built until the introduction of the Junior de Luxe in July 1961.
The Düsseldorf police incidentally also used a four-door Junior Sedan built by Auto Union as a patrol car for some time.
Once the DKW Junior de Luxe had been launched, the Junior 750 continued to be produced as an entry-level model. Visually the vehicle had not changed much - only the DKW coat of arms on the hood had been replaced with a DKW Junior logo. Production of the DKW Junior finally came to an end in December 1962.