FRANKFURT -- Volkswagen CEO Bernd Pischetsrieder's decision to resign had many analysts questioning today the role of VW Chairman Ferdinand Piech and Piech's company, Porsche.

"We conclude that his departure could be the result of significant differences on group strategy or resistance to the growing influence of Chairman Dr. Piech and Porsche CEO Dr. (Wendelin) Wiedeking," Goldman Sachs wrote in a research note.

Volkswagen surprised equity markets late on Tuesday, Nov. 7, not just by announcing Pischetsrieder would step down by year's end to be replaced by his boss's closest ally, Audi CEO Martin Winterkorn, but also by its refusal to give any reason for the departure.

At the center of the affair, analysts believe, stands Piech, Volkswagen's powerful chairman and former CEO sometimes referred to in the media as "the Godfather".

Piech, grandson of VW Beetle developer Ferdinand Porsche, is set to step down as head of VW's supervisory board next year.

Yet the Salzburg resident has left open if he will seek to retain a seat on the board, and a power struggle over Porsche's influence at VW could have prompted Pischetsrieder to leave after the VW CEO had pledged to keep Porsche "at arm's length".

When Porsche first got a stake in Volkswagen last year, it demanded and later got boardroom representation in line with its 20 percent holding. Porsche CEO Wiedeking and his finance head, Holger Haerter, joined the 20-person VW supervisory board.

TAKEOVER

Since Porsche has never ruled out raising its interest in VW to just below the percent threshold at which the sports car maker would have to launch a public takeover offer, Piech could be pinning hopes on Porsche consolidating his power by receiving a third seat if it raises its stake to just below 30 percent.

"A combination of Porsche's shareholding and supervisory board seats, together with Piech's continuing clout at VW, may have forced VW to accept deals on the Cayenne 2 or Panamera production contracts for Porsche that were not 100 percent acceptable to VW operational management," Credit Suisse wrote.

VW builds the Cayenne SUV for Porsche at a plant in Slovakia and has agreed to provide bodies for the four-door Panamera.

Citing a recent decision by Porsche shareholders to pool their holdings into two Salzburg-based vehicles that together own Porsche's VW stake, Morgan Stanley believed Piech's co-owned company has longer-term interests in Volkswagen.

"We cannot help but to view this move as 'stage two' of Porsche's growing influence over VW," the bank wrote.

Analysts also speculate that Porsche may attempt to buy Volkswagen outright, or at least some 58 percent in free float.

"Though odd, it's doable," Dresdner Kleinwort wrote.

Goldman estimated Porsche could theoretically pay between 89 and 123 euros per ordinary VW share, or about $114 to $157 at current exchange rates, and that the plans could have led to Pischetsrieder's abrupt departure.

"We believe this could be the prelude to a potential finalization of Porsche's intentions towards VW given its growing cash position (i.e., potential buy out)," the bank said.

Some analysts have focused on whether Piech and Wiedeking may be plotting to swap Porsche's stake in Volkswagen for control of Audi, where the VW chairman was once CEO.

Often territorial toward his successors, the Porsche scion saw to it that successors Herbert Demel and Franz-Josef Paeffgen resigned as Audi CEOs, and ultimately sent his chief lieutenant, Winterkorn, to look after the pearl of the Volkswagen empire.