Exhibit 99

JOINT FILING AGREEMENT

In accordance with Rule 13d-1(k)(1) promulgated under the Securities Exchange Act of 1934, as amended, the undersigned hereby agree to the joint filing with each other on behalf of each of them of such a statement on Schedule 13G with respect to the common stock beneficially owned by each of them of Allison Transmission Holdings, Inc. This Joint Filing Agreement shall be included as an Exhibit to such Schedule 13G.

IN WITNESS WHEREOF, the undersigned hereby execute this Joint Filing Agreement as of the 14th day of February, 2013.

CARLYLE GROUP MANAGEMENT L.L.C.
By:	/s/ Jeremy W. Anderson, attorney-in-fact
Name:	Daniel D’Aniello
Title:	Chairman
THE CARLYLE GROUP L.P.
By: Carlyle Group Management L.L.C., its general partner
By:	/s/ Jeremy W. Anderson, attorney-in-fact
Name:	Daniel D’Aniello
Title:	Chairman
CARLYLE HOLDINGS I GP INC.
By:	/s/ Jeremy W. Anderson, attorney-in-fact
Name:	Daniel D’Aniello
Title:	Chairman
CARLYLE HOLDINGS I GP SUB L.L.C.
By: Carlyle Holdings I GP Inc., its managing member
By:	/s/ Jeremy W. Anderson, attorney-in-fact
Name:	Daniel D’Aniello
Title:	Chairman
CARLYLE HOLDINGS I L.P.
By: Carlyle Holdings I GP Sub L.L.C., its general partner
By: Carlyle Holdings I GP Inc., its managing member
By:	/s/ Jeremy W. Anderson, attorney-in-fact
Name:	Daniel D’Aniello
Title:	Chairman

TC GROUP, L.L.C.
By: Carlyle Holdings I L.P., its managing member
By:	/s/ Jeremy W. Anderson, attorney-in-fact
Name:	Daniel D’Aniello
Title:	Chairman
TC GROUP SUB L.P.
By: TC Group, L.L.C., its general partner
By: Carlyle Holdings I L.P., its managing member
By:	/s/ Jeremy W. Anderson, attorney-in-fact
Name:	Daniel D’Aniello
Title:	Chairman
TC GROUP IV MANAGING GP, L.L.C.
By:	/s/ Jeremy W. Anderson
Name:	Jeremy W. Anderson
Title:	Authorized Person
CARLYLE PARTNERS IV AT HOLDINGS, L.P.
By: TC Group IV Managing GP, L.L.C., its general partner
By:	/s/ Jeremy W. Anderson
Name:	Jeremy W. Anderson
Title:	Authorized Person