INDIANAPOLIS, April 15, 2013 /PRNewswire/ -- Allison Transmission Holdings, Inc. (NYSE: ALSN), the world's largest manufacturer of fully-automatic transmissions for medium- and heavy-duty commercial vehicles, medium- and heavy-tactical U.S. defense vehicles and hybrid-propulsion systems for transit buses, announced today a proposed secondary offering of 22,000,000 shares of its common stock by investment funds affiliated with The Carlyle Group and Onex Corporation (the "Sponsors"). A group led by BofA Merrill Lynch, Citigroup and J.P. Morgan will act as the underwriters in the proposed registered public offering of those shares. In addition, the underwriters will have an option to purchase up to 3,300,000 additional shares from the Sponsors. All of the shares are being sold on a pro rata basis by the Sponsors, which are existing stockholders of Allison Transmission Holdings, Inc. ("Allison"), in accordance with their current interests. Following the offering, the Sponsors will continue to beneficially own an aggregate of approximately 128,697,499 shares, or approximately 70% in the aggregate, of Allison's outstanding common stock after giving effect to the offering (or approximately 125,397,499 shares, or approximately 68% in the aggregate if the underwriters fully exercise their option to purchase additional shares). The total number of outstanding shares of Allison's common stock will not change as a result of the offering. (Logo: http://photos.prnewswire.com/prnh/20120702/DE33547LOGO) A copy of the preliminary prospectus related to the offering may be obtained, when available, from BofA Merrill Lynch, 222 Broadway, New York, NY 10038, Attn: Prospectus Department, or e-mail email@example.com; Citigroup, c/o Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, NY 11717 (tel: 800-831-9146); and J.P. Morgan Securities LLC, Attention: Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, NY 11717, telephone: 866-803-9204. This press release shall not constitute an offer to sell or the solicitation of an offer to buy, nor shall there be any sale of these securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.