The tight and mutually beneficial relationship between Ford and Mazda has been an exemplar of symbiosis in the auto industry, but now that Ford has sold off its controlling interest in Mazda, that cooperation may be difficult or impossible due to legal roadblocks.

Already the two companies are erecting walls across previous open paths, including Mazda barring Ford staff from meetings and Ford's refusal to share confidential information with Mazda employees, reports The Detroit News.

Much of the new-found artificial divide between Mazda and Ford is due to legal requirements and anti-trust concerns - two legally independent companies operating in concert could be subject to serious liability that might not otherwise exist if they retained their former shareholder relationship. Nevertheless, both companies are eager to preserve their good working relationship.

"We have changed the ownership, but our intention is to continue to learn from each other," said Derrick Kuzak, Ford's global head of product development. "It's clear how much we at Ford value the partnership with Mazda."

"It has been the most successful alliance in automotive history," said Jim O'Sullivan, president of Mazda North America.

Unfortunately the divide could impair operations of both companies significantly: Mazda would be hampered by any further separating because of the difficulty in acquiring necessary materials and components in their relatively small-volume lots; Ford on the other hand would be handicapped by the lack of Mazda's design and engineering expertise, especially in the field of small cars.

Ford's sale of its controlling interest in Mazda was the result of its plan to preserve its viability and maximize its cash flow by liquidating assets in late 2008. That plan has served it well - it is the only U.S. carmaker not in need of federal loan support - but now that ties with Mazda appear to be under threat, that plan could have consequences and costs that weren't fully understood at the time.

For example, plans to bring the Mazda2 to the U.S. and the continued sharing of platforms between the two companies could be at risk, and it could ultimately mean the end of a partnership that has spanned nearly 40 years.