The legendary demonstration by the NSU staff on 18 April 1975, which became known as the "March on Heilbronn", was a semi-spontaneous action. Initially, the only thing that was certain was that a works meeting was to take place that day after the break for vespers. The Heilbronn plant workers were also to start an action, possibly a protest march into the city. When a works council member from Heilbronn called the gatekeeper at the Neckarsulm plant, this was the starting signal for the Neckarsulm workers as well and the gates were opened.

"The team marched, and all of them without exception: the female colleagues in high heels, the men in mechanics' suits." Klaus Zwickel, chairman of the Neckarsulm IG Metall union

On the morning of 18 April 1975, around 7,000 workers set off on a four-hour protest march to Heilbronn to demonstrate once again against the VW group's plans for cutbacks and to persuade the Audi-NSU supervisory board to reject the specifications from Wolfsburg. The route led out of Neckarsulm, on the B27 towards Heilbronn. After a rally on the market square, the workers marched to the avenue and then back towards Neckarsulm. After almost four hours, the colleagues returned to the Neckarsulm plant exhausted, some barefoot.

This march, which was widely reported in the media, was the culmination of IG Metall's efforts to mobilise the public for the fight to save jobs in Neckarsulm.

At the same time, this march was associated with a high risk for each individual participant. The management, including the then plant manager August Rappold and the personnel manager H.F. von Knobelsdorf warned on a notice in the plant: "A work stoppage and even more so leaving the plant premises during working hours are violations of the agreed [...] with the measures that may become necessary as a result."

Whether the march had helped to reinforce the measures that had basically already been decided may be left open. For the Neckarsulm plant, for the entire region, it was a sign of solidarity and cohesion that still characterises and distinguishes the workforce at the Audi Neckarsulm plant today.