Document:

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                                                                   Exhibit 4-b-1

                          FIRST SUPPLEMENTAL INDENTURE

         FIRST SUPPLEMENTAL INDENTURE, dated as of July 7, 2000, to the
Indenture, dated as of April 1, 1998, between Meritor Automotive, Inc., a
Delaware corporation ("Meritor") having its principal office at 2135 West Maple
Road, Troy, Michigan 48084-7186, and The Chase Manhattan Bank, a New York
banking corporation, as trustee (the "Trustee"), having its principal corporate
trust office at 450 West 33rd Street, 15th Floor, New York, New York 10001-2697,
Attention: Capital Markets Fiduciary Services (the "Indenture"). All capitalized
terms not defined herein are used herein as defined in the Indenture.

         WHEREAS, Meritor, Arvin Industries, Inc. ("Arvin"), and ArvinMeritor,
Inc. ("ArvinMeritor") have entered into an Agreement and Plan of Reorganization,
dated April 6, 2000, under which Meritor and Arvin will each merge into
ArvinMeritor, an Indiana corporation (the "Merger"); and

         WHEREAS, Section 8.01 of the Indenture provides that Meritor may merge
into any other corporation that is organized and existing under the laws of any
State if certain other conditions are satisfied; and

         WHEREAS, on February 24, 1999, Meritor issued $500,000,000 aggregate
principal amount of its 6.80% Notes due February 15, 2009 (the "Notes") under
the Indenture, and the Notes are outstanding on the date hereof; and

         WHEREAS, in connection with the Merger, ArvinMeritor will assume
Meritor's obligations under the Indenture, including its obligations with
respect to the Notes;

         NOW, THEREFORE, THIS SUPPLEMENTAL INDENTURE WITNESSETH:

         1. Effective upon consummation of the Merger, ArvinMeritor hereby
expressly assumes the due and punctual payment of the principal of (and premium,
if any) and interest, if any, on all the Securities and coupons, if any,
appertaining thereto and the performance of every covenant of the Indenture on
the part of Meritor to be performed or observed.

         2. Pursuant to Section 8.02 of the Indenture, upon consummation of the
Merger, ArvinMeritor shall succeed to, and be substituted for, and may exercise
every right and power of, the Company under the Indenture with the same effect
as if ArvinMeritor had been named as the Company in the Indenture, and
thereafter Meritor shall be relieved of all obligations and covenants under the
Indenture, the Securities and any coupons.

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         IN WITNESS WHEREOF, the parties hereto have caused this Supplemental
Indenture to be duly executed, and their respective corporate seals to be
hereunder affixed and attested, all as of the day and year first above written.

<TABLE>
<S>                                  <C>
[CORPORATE SEAL]                     MERITOR AUTOMOTIVE, INC.

                                     By: /s/ Vernon G. Baker, II
                                         ------------------------------
                                     Title: Senior Vice President, General
                                              Counsel and Secretary
Attest:

/s/ Bonnie Wilkinson
---------------------
Title: Assistant Secretary

[CORPORATE SEAL]                     ARVINMERITOR, INC.

                                     By:  /s/ Thomas A. Madden
                                        ----------------------
                                     Title: Senior Vice President and
                                              Chief Financial Officer
Attest:

/s/ Vernon G. Baker, II
-----------------------
Title: Secretary

[CORPORATE SEAL]                     THE CHASE MANHATTAN BANK, as Trustee

                                     By: /s/ Robert S. Peschler
                                         ----------------------
                                     Title: Assistant Vice President
Attest:

/s/ Diane Darconte
------------------
Authorized Officer
</TABLE><PAGE>   1

                                                                   Exhibit 4-c-1

                          SECOND SUPPLEMENTAL INDENTURE

                  Second Supplemental Indenture, dated as of July 7, 2000
("Second Supplemental Indenture"), between ARVINMERITOR, INC., an Indiana
corporation (hereinafter called the "Company"), having its principal executive
office at 2135 West Maple Road, Troy, Michigan 48084-7186, and Harris Trust and
Savings Bank, a banking organization organized under the laws of Illinois,
having its Corporate Trust Office at 2 North LaSalle Street, Suite 1020,
Chicago, Illinois 60602 ("Harris"), or any successor to Harris, as trustee
(hereinafter called the "Trustee").

                             RECITALS OF THE COMPANY

         On April 6, 2000, Arvin Industries, Inc., an Indiana corporation
("Arvin"), Meritor Automotive, Inc., a Delaware corporation ("Meritor"), and the
Company executed an agreement and plan of reorganization (the "Merger
Agreement") under which Meritor is being merged with and into the Company, to be
immediately followed by the merger of Arvin with and into the Company, with the
Company as the surviving corporation (the "Merger"). Arvin and the Trustee are
parties to that certain indenture dated as of July 3, 1990, as supplemented by
that First Supplemental Indenture dated as of March 31, 1994 (together, the
"Indenture"). In accordance with Section 801 of the Indenture, immediately
following the Merger, the Company is not in default in the performance or
observance of any of the terms, covenants and conditions of the Indenture to be
kept or performed by the Company; the Company is a corporation organized under
the laws of the State of Indiana; and the Company shall, by virtue of this
Second Supplemental Indenture, expressly assume the due and punctual payment of
the principal of and premium, if any, and interest on all of the Securities,
according to their tenor, and the due and punctual performance and observance of
all of the covenants and conditions of the Indenture to be performed or observed
by the Company. Section 901(1) of the Indenture authorizes the Company and the
Trustee (without the consent of any Holders of Securities issued under the
Indenture) to enter into a supplemental indenture for the purpose of evidencing
the succession of another Person to the Company, and the assumption by any such
successor of the covenants of the Company in the Indenture and in the Securities
contained. The Company now proposes to enter into this Second Supplemental
Indenture for the purpose of evidencing the succession of the Company to Arvin
and the assumption by the Company of the covenants of Arvin in the Indenture and
in the Securities contained.

             NOW, THEREFORE, THIS SUPPLEMENTAL INDENTURE WITNESSETH:

         For and in consideration of the premises and for the equal and
proportionate benefit of all Holders of Securities heretofore or hereafter
authenticated and delivered under the Indenture, it is mutually covenanted and
agreed as follows:

         1.       The Company expressly assumes the due and punctual payment of
                  the principal of and premium, if any, and interest on all of
                  the Securities, according to their tenor, and the due and
                  punctual performance and observance of all of the covenants
                  and conditions of the Indenture to be performed or observed by
                  the Company.

         2.       This Second Supplemental Indenture shall become operative and
                  effective upon the merger of Arvin with and into the Company,
                  as contemplated by the Merger Agreement.

         3.       Pursuant to Section 904 of the Indenture, (i) the Indenture is
                  modified in accordance with the provisions of this
                  Supplemental Indenture, (ii) this Second Supplemental
                  Indenture forms a part of the Indenture for all purposes, and
                  (iii)

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                  every Holder of Securities heretofore or hereafter
                  authenticated and delivered under the Indenture and of any
                  coupons appertaining thereto is bound by this Second
                  Supplemental Indenture.

         4.       References to the Indenture, including all such references in
                  Securities of any series heretofore or hereafter authenticated
                  and delivered under the Indenture, need not contain any
                  reference to this Second Supplemental Indenture, but all
                  references to the Indenture dated as of July 3, 1990, between
                  Arvin and Harris, or to the Indenture dated as of July 3,
                  1990, between Arvin and Harris, as amended by the First
                  Supplemental Indenture dated as of March 31, 1994, between
                  Arvin and Harris, shall be deemed to refer to the Indenture as
                  modified in accordance with this Second Supplemental
                  Indenture.

         5.       All capitalized terms used in this Second Supplemental
                  Indenture and not defined herein shall have the respective
                  meanings set forth in the Indenture. The recitals contained in
                  this Second Supplemental Indenture shall be taken as the
                  statements of the Company, and the Trustee assumes no
                  responsibility for their correctness. This instrument may be
                  executed in any number of counterparts, each of which so
                  executed shall be deemed to be an original, but all such
                  counterparts shall together constitute but one and the same
                  instrument.

         6.       This Second Supplemental Indenture may be executed in one or
                  more separate counterparts, each of which shall be an
                  original, but all of which together shall constitute one
                  instrument.

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         IN WITNESS WHEREOF, the parties hereto have caused this Second
Supplemental Indenture to be duly executed, and their respective corporate seals
to be hereunto affixed, all as of the day and year first above written.

<TABLE>
<S>                                      <C>
                                         ARVINMERITOR, INC.

                                         By:      /s/ Thomas A. Madden
                                                  --------------------
[SEAL]                                   Name:    Thomas A. Madden
                                         Its:     Senior Vice President, Chief Financial
                                                  Officer and Treasurer
ATTEST:

By:      /s/ Vernon G. Baker, II
         -----------------------
         Secretary

                                         HARRIS TRUST AND SAVINGS BANK, not in its
                                         individual capacity but solely as trustee

                                         By:      /s/ J. Bartolini
                                                  ----------------
[SEAL]                                   Name:    J. Bartolini
                                         Its:     Authorized Officer
ATTEST:

By:      /s/ C. H. Long
         --------------
         Assistant Secretary
</TABLE>

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