X0304 4 2012-03-20 0001411207 Allison Transmission Holdings Inc ALSN 0001022596 TCG HOLDINGS LLC C/O THE CARLYLE GROUP 1001 PENNSYLVANIA AVE. NW, SUITE 220S WASHINGTON DC 20004 0 0 1 0 0000933790 TC Group, LLC C/O THE CARLYLE GROUP 1001 PENNSYLVANIA AVE. NW, SUITE 220S WASHINGTON DC 20004 0 0 1 0 0001468089 TC Group IV Managing GP, L.L.C. C/O THE CARLYLE GROUP 1001 PENNSYLVANIA AVE. NW, SUITE 220S WASHINGTON DC 20004 0 0 1 0 0001544355 Carlyle Partners IV AT Holdings, L.P. C/O THE CARLYLE GROUP 1001 PENNSYLVANIA AVE. NW, SUITE 220S WASHINGTON DC 20004 0 0 1 0 Common Stock 2012-03-20 4 S 0 15007500 21.74 D 75348750 I See Footnote By Carlyle Partners IV AT Holdings, L.P. TC Group IV Managing GP, L.L.C. is the general partner of Carlyle Partners IV AT Holdings, L.P. TC Group, L.L.C. is the managing member of TC Group IV Managing GP, L.L.C. TCG Holdings, L.L.C. is the managing member of TC Group, L.L.C. Accordingly, each of TC Group IV Managing GP, L.L.C., TC Group, L.L.C. and TCG Holdings, L.L.C. may be deemed to be beneficial owners of shares of common stock owned of record by Carlyle Partners IV AT Holdings, L.P. TCG Holdings, L.L.C. is managed by a three-person managing board, and all board action relating to the voting or disposition of these shares requires approval of a majority of the board. William E. Conway, Jr., Daniel A. D'Aniello and David M. Rubenstein, as the managing members of TCG Holdings, L.L.C., may be deemed to share beneficial ownership of shares of common stock beneficially owned by TCG Holdings, L.L.C. Such individuals expressly disclaim any such beneficial ownership. Exhibit List: Exhibit 99 - Joint Filer Information /s/ Jeremy W. Anderson, attorney-in-fact 2012-03-22