FIRST SUPPLEMENTAL INDENTURE

EXHIBIT 4.4

FIRST SUPPLEMENTAL INDENTURE

FIRST SUPPLEMENTAL INDENTURE (this “Supplemental Indenture”) dated as of January 29, 2015, among Grede LLC (the “Guarantor”) and Wilmington Trust, National Association, as trustee (the “Trustee”) under the Indenture dated as of October 20, 2014 among MPG Holdco I Inc., a Delaware corporation (the “Company”), the guarantors party thereto, and the Trustee (as amended, supplemented or otherwise modified, the “Indenture”).

W I T N E S S E T H

WHEREAS the Company has heretofore executed and delivered to the Trustee the Indenture, providing initially for the issuance of $600,000,000 in aggregate principal amount of the Company’s 7.375% Senior Notes due 2022 (the “Notes”);

WHEREAS Sections 4.11 and 10.07 of the Indenture provide that under certain circumstances the Company is required to cause the Guarantor to execute and deliver to the Trustee a supplemental indenture pursuant to which the Guarantor shall unconditionally guarantee all the Company’s Obligations under the Notes and the Indenture pursuant to a Guarantee on the terms and conditions set forth herein; and

WHEREAS pursuant to Section 9.01 of the Indenture, the Trustee and the Company are authorized to execute and deliver this Supplemental Indenture;

NOW THEREFORE, in consideration of the foregoing and for other good and valuable consideration, the receipt of which is hereby acknowledged, the Guarantor and the Trustee mutually covenant and agree for the equal and ratable benefit of the Holders as follows:

1. Defined Terms. As used in this Supplemental Indenture, terms defined in the Indenture or in the preamble or recital hereto are used herein as therein defined, except that the term “Holders” in this Guarantee shall refer to the term “Holders” as defined in the Indenture and the Trustee acting on behalf of and for the benefit of such Holders. The words “herein,” “hereof” and “hereby” and other words of similar import used in this Supplemental Indenture refer to this Supplemental Indenture as a whole and not to any particular section hereof.

2. Guarantee. The Guarantor hereby, jointly and severally with all existing Guarantors, irrevocably and unconditionally guarantees the Company’s Obligations under the Notes and the Indenture on the terms and subject to the conditions set forth in the Indenture, including, but not limited to, Article 10 of the Indenture, and agrees to be bound by all other applicable provisions of the Indenture and the Notes and to perform all of the obligations and agreements of a Guarantor under the Indenture.

3. Releases. The Guarantee of the Guarantor shall terminate and be of no further force or effect and the Guarantor shall be deemed to be released from all obligations as provided in Section 10.03 of the Indenture.

4. Notices. All notices or other communications to the Guarantor shall be given as provided in Section 11.02 of the Indenture.

5. Ratification of Indenture; Supplemental Indentures Part of Indenture. Except as expressly amended and supplemented hereby, the Indenture is in all respects ratified and confirmed and

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the terms, conditions and provisions thereof shall remain in full force and effect. This Supplemental Indenture shall form a part of the Indenture for all purposes, and every Holder of Notes heretofore or hereafter authenticated and delivered shall be bound hereby.

6. No Recourse Against Others. No past, present or future director, officer, employee, manager, incorporator, agent or holder of any Equity Interests in the Company or of the Guarantor or any direct or indirect parent corporation, as such, shall have any liability for any obligations of the Company and the Guarantor under the Notes, the Guarantee, the Indenture or this Supplemental Indenture or for any claim based on, in respect of, or by reason of, such obligations or their creation. Each Holder of Notes by accepting a Note waives and releases all such liability. The waiver and release are part of the consideration for issuance of the Notes. The waiver may not be effective to waive liabilities under the federal securities laws.

7. Governing Law. THIS SUPPLEMENTAL INDENTURE SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK. THE GUARANTOR AND THE TRUSTEE HEREBY IRREVOCABLY WAIVES, TO THE FULLEST EXTENT PERMITTED BY APPLICABLE LAW, ANY AND ALL RIGHT TO TRIAL BY JURY IN ANY LEGAL PROCEEDING ARISING OUT OF OR RELATING TO THIS SUPPLEMENTAL INDENTURE, THE INDENTURE, THE NOTES OR THE TRANSACTION CONTEMPLATED HEREBY.

8. Trustee Makes No Representation. The Trustee makes no representation as to the validity or sufficiency of this Supplemental Indenture.

9. Multiple Originals. The parties may sign any number of copies of this Supplemental Indenture. Each signed copy shall be an original, but all of them together represent the same agreement. One signed copy is enough to prove this Supplemental Indenture. The exchange of copies of this Supplemental Indenture and of signature pages by facsimile or email (in PDF format or otherwise) shall constitute effective execution and delivery of this Supplemental Indenture as to the parties hereto and may be used in lieu of the original Supplemental Indenture for all purposes. Signatures of the parties hereto transmitted by facsimile or email (in PDF format or otherwise) shall be deemed to be their original signatures for all purposes.

10. Effect of Headings. The Section headings herein are for convenience only and shall not affect the construction thereof.

11. The Trustee. The Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this Supplemental Indenture or for or in respect of the recitals or statements contained herein, all of which recitals and statements are made solely by the Guarantor.

12. Successors. All agreements of the Guarantor in this Supplemental Indenture shall bind its successors. All agreements of the Trustee in this Indenture shall bind its successors.

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IN WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture to be duly executed as of the date first above written.

[Signature Page to First Supplemental Indenture]

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