UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 OR 15(d)

of The Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): September 14, 2016

ALLISON TRANSMISSION HOLDINGS, INC.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code (317) 242-5000

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

Item 8.01 Other Events.

On September 14, 2016, Allison Transmission Holdings, Inc. (the “Company”) announced that its wholly owned subsidiary, Allison Transmission, Inc. (the “Issuer”), commenced its previously announced offering of $500 million in aggregate principal amount of senior unsecured notes due 2024 (the “Notes”) in a private placement (the “Offering”) exempt from registration under the Securities Act of 1933, as amended (the “Securities Act”), subject to market conditions. The Notes will be guaranteed by each of the Issuer’s existing and future domestic subsidiaries that is a borrower under or that guarantees obligations under the Issuer’s senior secured credit facility, subject to certain exceptions, but will not be guaranteed by the Company. On the issue date, it is expected that none of the Issuer’s domestic subsidiaries will guarantee its obligations under the Issuer’s senior secured credit facility, and therefore none of the Issuer’s domestic subsidiaries will initially guarantee the Notes. The Issuer intends to use the net proceeds from the Offering, together with cash on hand, to repay approximately $700 million of its outstanding term loans and pay related transaction fees and expenses.

A copy of the press release is attached hereto as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated by reference herein. The foregoing description does not purport to be complete and is qualified in its entirety by reference to such Exhibit.

This Current Report is for information purposes only and is neither an offer to sell nor a solicitation of an offer to buy any security. The Notes will not be registered under the Securities Act and may not be offered or sold in the United States absent registration or an applicable exemption from the registration requirements.

This Current Report contains forward-looking statements. All statements other than statements of historical fact contained in this Current Report are forward-looking statements. In some cases, you can identify forward-looking statements by terminology such as “may,” “will,” “should,” “expect,” “plans,” “project,” “anticipate,” “believe,” “estimate,” “predict,” “intend,” “forecast,” “could,” “potential,” “continue” or the negative of these terms or other similar terms or phrases. Forward-looking statements are not guarantees of future performance and involve known and unknown risks. Factors which may cause the actual results to differ materially from those anticipated at the time the forward-looking statements are made include, but are not limited to: risks related to the Offering, including that such transactions may not occur; risks related to our substantial indebtedness; our participation in markets that are competitive; the highly cyclical industries in which certain of our end users operate; the failure of markets outside North America to increase adoption of fully-automatic transmissions; the concentration of our net sales in our top five customers and the loss of any one of these; future reductions or changes in government subsidies for hybrid vehicles; future reductions or changes in U.S. defense spending; general economic and industry conditions; the discovery of defects in our products, resulting in delays in new model launches, recall campaigns and/or increased warranty costs and reduction in future sales or damage to our brand and reputation; our ability to prepare for, respond to and successfully achieve our objectives relating to technological and market developments and changing customer needs; risks associated with our international operations; labor strikes, work stoppages or similar labor disputes, which could significantly disrupt our operations or those of our principal customers; and other risks and uncertainties associated with our business described in our Annual Report on Form 10-K, Quarterly Reports on Form 10-Q and Current Reports on Form 8-K. Although we believe the expectations reflected in such forward-looking statements are based upon reasonable assumptions, we can give no assurance that the expectations will be attained or that any deviation will not be material. All information is as of the date of this Current Report, and we undertake no obligation to update any forward-looking statement to conform the statement to actual results or changes in expectations.

Item 9.01. Financial Statements and Exhibits

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

EXHIBIT INDEX