Allison Transmission Holdings Inc. sold more shares than expected in a $600.3 million initial public offering that priced within range on Wednesday, according to an underwriter.

Reuters reported that the Indianapolis-based maker of automatic transmissions for trucks, buses and military vehicles sold 26.1 million shares at $23 apiece, versus estimates for 21.7 million shares at a range of $22 to $24.

Allison closed its books a day ahead of schedule due to strong demand, according to two underwriters.

Allison was sold by General Motors to private equity firms Carlyle and Onex in 2007 for $5.6 billion. It holds a 62% market share of the global market for medium and heavy duty commercial vehicles.

In 2011, Allison’s earnings topped $103 million, compared with a profit of $30 million in the prior year. Net sales grew 12% to $2.2 billion.

It will pay a dividend of 6 cents a share beginning in the second quarter.

Both Carlyle and Onex sold all of the shares in the IPO, and Allison did not receive any proceeds. They will each hold a 43%stake in Allison after the offering.

Allison’s offering could pave the way for other auto parts manufacturers to go public. Electric motor maker Remy International filed for an IPO of up to $100 million in March 2011, while Affinia filed for a $230 million offering in June 2010.

Much of Allison’s growth has come from an industrywide rebound in truck sales.