Clearwire co-founder and former CEO Ben Wolff has quit his post on the company’s board of directors, ending his seven-year stint at the WiMAX operator.

The resignation “is not due to any disagreements with the company on any matters relating to the company’s operations, policies or practices,” the company said in documents filed Friday with the SEC. No further details were provided about his departure.

Wolff was first nominated to his post on the company’s 12-member board in 2008. Eagle River Holdings, an investment firm owned by Clearwire’s other co-founder Craig McCaw, expects to nominate Wolff’s replacement.

Wolff held a variety of posts at Clearwire, including executive vice president, president, CEO and co-chairman of the board of directors. He left his CEO post in 2009 and was replaced by industry veteran Bill Morrow, who resigned two years later. Board chairman John Stanton served as interim CEO until this August, when COO Erik Prusch was appointed to the post.

Wolff’s departure comes at a critical junction for Clearwire. The primary customer for its wholesale WiMAX service, Sprint, recently announced that it will stop using Clearwire’s network in favor of its own LTE network beginning next year. Meanwhile, Clearwire is trying to raise the $600 million it needs to overlay its network with TD-LTE. Sprint will eventually lease extra LTE capacity from Clearwire, helping to offset the loss of wholesale WiMAX revenue.

Sprint is Clearwire’s largest shareholder. The two operators have had disagreements about strategy and funding, but the LTE partnership announced last week suggests their relationship is improving.