SEC Form 4

FORM 4		UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* ONEX CORP (Last) (First) (Middle) C/O ONEX CORPORATION 161 BAY STREET (Street) TORONTO A6 M5J 2S1 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol Allison Transmission Holdings Inc [ ALSN ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)
	3. Date of Earliest Transaction (Month/Day/Year) 03/20/2012
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	03/20/2012		S		15,007,500	D	$21.74	75,348,749	I	See footnotes(1)(2)(3)(4)(5)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

1. Name and Address of Reporting Person* ONEX CORP (Last) (First) (Middle) C/O ONEX CORPORATION 161 BAY STREET (Street) TORONTO A6 M5J 2S1 (City) (State) (Zip)

1. Name and Address of Reporting Person* SCHWARTZ GERALD W (Last) (First) (Middle) C/O ONEX CORPORATION 161 BAY STREET (Street) TORONTO A6 M5J 2S1 (City) (State) (Zip)

1. Name and Address of Reporting Person* Onex American Holdings II LLC (Last) (First) (Middle) C/O ONEX CORPORATION 161 BAY STREET (Street) TORONTO A6 M5J 2S1 (City) (State) (Zip)

1. Name and Address of Reporting Person* Onex American Holdings GP LLC (Last) (First) (Middle) C/O ONEX CORPORATION 161 BAY STREET (Street) TORONTO A6 M5J 2S1 (City) (State) (Zip)

1. Name and Address of Reporting Person* Allison Executive Investco LLC (Last) (First) (Middle) C/O ONEX CORPORATION 161 BAY STREET (Street) TORONTO A6 M5J 2S1 (City) (State) (Zip)

1. Name and Address of Reporting Person* Allison Executive Investco II LLC (Last) (First) (Middle) C/O ONEX CORPORATION 161 BAY STREET (Street) TORONTO A6 M5J 2S1 (City) (State) (Zip)

1. Name and Address of Reporting Person* Onex American Holdings Subco LLC (Last) (First) (Middle) C/O ONEX CORPORATION 161 BAY STREET (Street) TORONTO A6 M5J 2S1 (City) (State) (Zip)

1. Name and Address of Reporting Person* OAH Wind LLC (Last) (First) (Middle) C/O ONEX CORPORATION 161 BAY STREET (Street) TORONTO A6 M5J 2S1 (City) (State) (Zip)

1. Name and Address of Reporting Person* Onex Allison Holding Ltd S.A.R.L. (Last) (First) (Middle) C/O ONEX CORPORATION 161 BAY STREET (Street) TORONTO A6 M5J 2S1 (City) (State) (Zip)

Explanation of Responses:

1. Includes: (i) 34,064,491 shares of common stock held by Onex Partners II LP; (ii) 22,901,322 shares of common stock held by Onex Allison Holding Limited S.a R.L.; (iii) 16,057,930 shares of common stock held by Onex Allison Co-Invest LP; (iv) 641,740 shares of common stock held by Onex US Principals LP; and (v) 320,170 shares of common stock held by Onex Partners II GP LP.

2. Onex Corporation may be deemed to beneficially own the common stock held by (a) Onex Partners II LP, through Onex Corporation's ownership of all of the common stock of Onex Partners GP Inc., the general partner of Onex Partners II GP LP, the general partner of Onex Partners II LP; (b) Onex Allison Holding Limited S.a R.L., through Onex Corporation's ownership of all of the equity of Onex American Holdings II LLC, which owns all of the equity of each of Allison Executive Investco LLC, which owns all of the equity of Allison Executive Investco II LLC, and Onex American Holdings Subco LLC, which owns all of the equity of OAH Wind LLC, which OAH Wind LLC and Allison Executive Investco II LLC own all of the equity of Onex Allison Holding Limited S.a R.L.; (continued)

3. (c) Onex Allison Co-Invest LP, through Onex Corporation's ownership of all of the common stock of Onex Partners GP Inc., the general partner of Onex Partners II GP LP, the general partner of Onex Allison Co-Invest LP; (d) Onex US Principals LP, through Onex Corporation's ownership of all of the equity of Onex American Holdings II LLC, which owns all of the equity of Onex American Holdings GP LLC, the general partner of Onex US Principals LP; and (e) Onex Partners II GP LP, through Onex Corporation's ownership of all of the common stock of Onex Partners GP Inc., the general partner of Onex Partners II GP LP.

4. Also includes 1,361,911 shares of common stock and 1,185 shares of non-voting common stock held by 1597257 Ontario Inc., an independent entity that is controlled by Mr. Gerald W. Schwartz. Mr. Schwartz, the Chairman, President and Chief Executive Officer of Onex Corporation, owns shares representing a majority of the voting rights of the shares of Onex Corporation and as such may be deemed to own beneficially all of the common stock and non-voting common stock owned beneficially by Onex Corporation. Mr. Schwartz disclaims such beneficial ownership, except to the extent of his pecuniary interest therein. Mr. Schwartz has indirect voting and investment control of Onex Corporation.

5. Due to the limitations of the electronic filing system, Onex Partners GP Inc., Onex US Principals LP, Onex Partners II GP LP, Onex Allison Co-Invest LP, Onex Partners II LP, 1597257 Ontario Inc., Onex Advisor III LLC and Onex Advisor Subco LLC are filing a separate Form 4.

Remarks:

Exhibit List: Exhibit 99 - Joint Filer Information

	/s/ Andrea E. Daly, Authorized Person	03/22/2012
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
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