Document:

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                                                                    Exhibit 4(q)

AMENDMENT NO. 8

                      EIGHTH AMENDMENT TO THIRD AMENDED AND
                       RESTATED REVOLVING CREDIT AGREEMENT

         THIS EIGHTH AMENDMENT, dated as of the 8th day of December, 2000, by
and between Newcor, Inc., a Delaware corporation, of Bloomfield Hills, Michigan
(herein called "Company") and Comerica Bank, a Michigan banking corporation, of
Detroit, Michigan (herein called "Bank");

                                   WITNESSETH:

         WHEREAS, Company and Bank desire to amend that certain Third Amended
and Restated Revolving Credit Agreement dated as of January 15, 1998, entered
into by and between Company and Bank, which was amended by seven amendments
(herein called "Agreement");

         NOW, THEREFORE, it is agreed that the Agreement is amended as follows:

         1.       The definition of "Revolving Credit Maturity Date" in Section
                  1 of the Agreement is amended to read in its entirety:

                  "`Revolving Credit Maturity Date' shall mean June 1, 2001."

         2.       The definition of "Base Net Worth" in Section 1 of the
                  Agreement is amended to read in its entirety as follows:

                  "`Base Net Worth' shall mean, $5,000,000. On the last day of
         each fiscal quarter of Company commencing December 31, 2000, Base Net
         Worth shall be increased by an amount equal to 50% of Net Income for
         the fiscal quarter then ended. Such increase shall be effective on the
         last day of the fiscal quarter in which such determination is made. Any
         fiscal quarter with respect to which Net Income is less than zero, Net
         Income shall be deemed to be zero."

         3.       Section 6.4 of the Agreement is amended to read in its
                  entirety as follows:

                  "On a consolidated statement basis, maintain as of the end of
         each fiscal quarter, a Funded Debt to EBITDA Ratio of not more than 8.0
         to 1.0."

         4.       Company hereby represents and warrants that, after giving
         effect to the amendment contained herein, (a) execution, delivery and
         performance of this Amendment and any other documents and instruments
         required under this Amendment or the Agreement are within Company's
         corporate powers, have been duly authorized, are not in contravention
         of law or the terms of Company's Certificate of Incorporation or
         Bylaws, and do not require the consent or approval of any governmental
         body, agency, or authority; and this Amendment and any other documents
         and instruments required under this Amendment or the Agreement, will be
         valid and binding in accordance with their terms; (b) the continuing
         representations and warranties of Company set forth in Sections 5.1
         through 5.7 and 5.9 through 5.15 of the Agreement are true and correct
         on and as of the date hereof with the same force and effect as made on
         and as of the date hereof; (c) the continuing representations and
         warranties of Company set forth in Section 5.8 of the Agreement are
         true and correct as of the date hereof with respect to the most recent
         financial statements furnished to the Bank by Company in accordance
         with Section 6.1 of the Agreement; and (d) no event of default, or
         condition or event which, with the giving of notice or the running of
         time, or both, would constitute an event of default under the
         Agreement, has occurred and is continuing as of the date hereof.

         5.       This Amendment shall be effective upon (a) execution of this
         Amendment by Company and Bank (b) execution by the Guarantors of the
         attached Acknowledgment, and (c) payment by Company to Bank of a
         non-refundable $15,000 amendment and waiver fee.

<PAGE>   2
         6.       Except as modified hereby, all of the terms and conditions of
         the Agreement shall remain in full force and effect.

         WITNESS the due execution hereof on the day and year first above
written.

COMERICA BANK                       NEWCOR, INC.

By:  /s/ Brian E.  Marshall         By:     /s/ James J. Connor
   ----------------------------        -----------------------------------------

Its: Vice President                 Its:   President and Chief Executive Officer
                                        ----------------------------------------

                                    By:      /s/ Thomas D. Parker
                                       -----------------------------------------

                                    Its:  Vice-President Human Resources and
                                            Secretary
                                        ----------------------------------------

<PAGE>   3

                                 ACKNOWLEDGMENT

         The undersigned accept and agree to the Amendment No. 8 to the Third
Amended and Restated Revolving Credit Agreement and agree to the continued
effectiveness of the Guaranties originally executed and delivered to Comerica
Bank by the undersigned on January 15, 1998 and on March 4, 1998, as applicable.

                              ROCHESTER GEAR, INC.

                              By:        /s/ James J. Connor
                                 ------------------------------------

                              Its:            President
                                  -----------------------------------

                              By:         /s/ Thomas D. Parker
                                 ------------------------------------

                              Its:          Secretary
                                  -----------------------------------

                              ENC CORP.

                              By:        /s/ James J. Connor
                                 ------------------------------------

                              Its:            President
                                  -----------------------------------

                              By:         /s/ Thomas D. Parker
                                 ------------------------------------

                              Its:          Secretary
                                  -----------------------------------

<PAGE>   4

DECO TECHNOLOGIES, INC.                     PLASTRONICS PLUS, INC.

By:  /s/ James J. Connor                  By:  /s/ James J. Connor
  -------------------------------           ------------------------------

Its:  President                           Its: President
      ---------------------------              ---------------------------

By:  /s/ Thomas D. Parker                 By:  /s/ Thomas D. Parker
    -----------------------------             ----------------------------

Its:  Secretary                           Its: Secretary
      ---------------------------              ---------------------------

DECO INTERNATIONAL, INC.                  NEWCOR M-T-L, INC.

By:  /s/ James J. Connor                  By:  /s/ James J. Connor
  -------------------------------           ------------------------------

Its:  President                           Its: President
      ---------------------------              ---------------------------

By:  /s/ Thomas D. Parker                 By:  /s/ Thomas D. Parker
    -----------------------------             ----------------------------

Its:  Secretary                           Its: Secretary
      ---------------------------              ---------------------------

TURN-MATIC, INC.                          GRAND MACHINING COMPANY

By:  /s/ James J. Connor                  By:  /s/ James J. Connor
  -------------------------------           ------------------------------

Its: President                            Its: President
    -----------------------------             ----------------------------

By:  /s/ Thomas D. Parker                 By:  /s/ Thomas D. Parker
    -----------------------------             ----------------------------

Its:  Secretary                           Its:  Secretary
      ---------------------------               --------------------------<PAGE>   1
                                                                    Exhibit 4(r)

AMENDMENT NO. 9

                      NINTH AMENDMENT TO THIRD AMENDED AND
                       RESTATED REVOLVING CREDIT AGREEMENT

         THIS NINTH AMENDMENT, dated as of the 25th day of January, 2001, by and
between Newcor, Inc., a Delaware corporation, of Bloomfield Hills, Michigan
(herein called "Company") and Comerica Bank, a Michigan banking corporation, of
Detroit, Michigan (herein called "Bank");

                                   WITNESSETH:

         WHEREAS, Company and Bank desire to amend that certain Third Amended
and Restated Revolving Credit Agreement dated as of January 15, 1998, entered
into by and between Company and Bank, which was amended by eight amendments
(herein called "Agreement");

         NOW, THEREFORE, it is agreed that the Agreement is amended as follows:

         1.       The definition of "Commitment" in Section 1 of the Agreement
                  is amended to read in its entirety as follows:

                  "`Commitment' shall mean the total commitment of Bank to make
         Advances to Company pursuant to this Agreement in the amount of Forty
         Million Dollars ($40,000,000), subject to reduction as herein
         provided."

         2.       The definition of "Revolving Credit Maturity Date" in Section
                  1 of the Agreement is amended to read in its entirety:

                  "`Revolving Credit Maturity Date' shall mean March 31, 2002."

         3.       The definition of "Base Net Worth" in Section 1 of the
                  Agreement is amended to read in its entirety as follows:

                  "`Base Net Worth' shall mean $3,000,000. On the last day of
         each fiscal quarter of Company (commencing March 31, 2001), Base Net
         Worth shall be increased by an amount equal to 50% of Net Income for
         the fiscal quarter then ended. Such increase shall be effective on the
         last day of the fiscal quarter in which such determination is made. For
         any fiscal quarter with respect to which Net Income is less than zero,
         Net Income shall be deemed to be zero."

         4.       The definition of "EBITDA" in Section 1 of this Agreement is
                  amended to read in its entirety as follows:

                  "`EBITDA' shall mean as of any date of determination, Net
         Income for the four preceding fiscal quarters ending on such date of
         determination, plus, to the extent deducted in determining Net Income,
         (1) depreciation and amortization expense of Company and its
         consolidated Subsidiaries for such period, (2) interest expense of
         Company and its consolidated Subsidiaries for such period, and (3)
         income taxes of Company and its consolidated Subsidiaries for such
         period, all as determined in accordance with generally accepted
         accounting principles consistently applied; provided that with respect
         to any period of determination which includes any portion of calendar
         year 2000 there shall be added to Net Income (to the extent deducted in
         determining Net Income during the applicable period) an amount equal to
         professional fees (in an aggregate amount not exceeding $2,450,000) and
         plant closure costs (in an aggregate amount not exceeding $1,400,000)."

         5.       Section 6.4 of the Agreement is amended to read in its
                  entirety as follows:

<PAGE>   2

                  "On a consolidated statement basis, maintain as of the end of
         each fiscal quarter, a Funded Debt to EBITDA Ratio of not more than
         10.0 to 1.0."

         6.       Company hereby represents and warrants that, after giving
         effect to the amendment contained herein, (a) execution, delivery and
         performance of this Amendment and any other documents and instruments
         required under this Amendment or the Agreement are within Company's
         corporate powers, have been duly authorized, are not in contravention
         of law or the terms of Company's Certificate of Incorporation or
         Bylaws, and do not require the consent or approval of any governmental
         body, agency, or authority; and this Amendment and any other documents
         and instruments required under this Amendment or the Agreement, will be
         valid and binding in accordance with their terms; (b) the continuing
         representations and warranties of Company set forth in Sections 5.1
         through 5.7 and 5.9 through 5.15 of the Agreement are true and correct
         on and as of the date hereof with the same force and effect as made on
         and as of the date hereof; (c) the continuing representations and
         warranties of Company set forth in Section 5.8 of the Agreement are
         true and correct as of the date hereof with respect to the most recent
         financial statements furnished to the Bank by Company in accordance
         with Section 6.1 of the Agreement; and (d) no event of default, or
         condition or event which, with the giving of notice or the running of
         time, or both, would constitute an event of default under the
         Agreement, has occurred and is continuing as of the date hereof.

         7.       This Amendment shall be effective upon (a) execution of this
         Amendment by Company and Bank (b) execution by the Guarantors of the
         attached Acknowledgment, and (c) delivery by Company to Bank of an
         executed Revolving Credit Note in the form attached hereto as Exhibit
         "A".

         8.       Except as modified hereby, all of the terms and conditions of
         the Agreement shall remain in full force and effect.

         WITNESS the due execution hereof on the day and year first above
written.

COMERICA BANK                   NEWCOR, INC.

By:  /s/ Brian E. Marshall      By:  /s/ James J. Connor
  -------------------------        ---------------------------------------------

Its: Vice President             Its:  President & Chief Executive Officer
                                    --------------------------------------------

                                By:   /s/ Thomas D. Parker
                                   ---------------------------------------------

                                Its:  Vice-President Human Resources & Secretary
                                    --------------------------------------------

<PAGE>   3

                                 ACKNOWLEDGMENT

         The undersigned accept and agree to the Amendment No. 9 to the Third
Amended and Restated Revolving Credit Agreement and agree to the continued
effectiveness of the Guaranties originally executed and delivered to Comerica
Bank by the undersigned guarantying all obligations of Newcor, Inc. to the Bank.

                                    ROCHESTER GEAR, INC.

                                    By:        /s/ James J. Connor
                                       ---------------------------------

                                    Its:            President
                                        --------------------------------

                                    By:         /s/ Thomas D. Parker
                                       ---------------------------------

                                    Its:          Secretary
                                        --------------------------------

                                    ENC CORP.

                                    By:        /s/ James J. Connor
                                       ---------------------------------

                                    Its:            President
                                        --------------------------------

                                    By:         /s/ Thomas D. Parker
                                       ---------------------------------

                                    Its:          Secretary
                                        --------------------------------

<PAGE>   4

DECO TECHNOLOGIES, INC.                 PLASTRONICS PLUS, INC.

By:  /s/ James J. Connor                By:  /s/ James J. Connor
  ----------------------------------       ------------------------------

Its:  President                         Its: President
    --------------------------------        ----------------------------

By:  /s/ Thomas D. Parker               By:  /s/ Thomas D. Parker
    --------------------------------       -----------------------------

Its:  Secretary                         Its: Secretary
      ------------------------------        ----------------------------

DECO INTERNATIONAL, INC.                NEWCOR M-T-L, INC.

By:  /s/ James J. Connor                By:  /s/ James J. Connor
  ----------------------------------      ------------------------------

Its: President                          Its: President
    --------------------------------        ----------------------------

By:  /s/ Thomas D. Parker               By:  /s/ Thomas D. Parker
    --------------------------------        ----------------------------

Its:  Secretary                         Its: Secretary
      ------------------------------         ---------------------------

TURN-MATIC, INC.                        GRAND MACHINING COMPANY

By:  /s/ James J. Connor                By:  /s/ James J. Connor
  ----------------------------------      ------------------------------

Its: President                          Its: President
    --------------------------------        ----------------------------

By:  /s/ Thomas D. Parker               By:  /s/ Thomas D. Parker
    --------------------------------        ----------------------------

Its:  Secretary                         Its: Secretary
      ------------------------------         ---------------------------

<PAGE>   5

                                   EXHIBIT "A"

                              REVOLVING CREDIT NOTE

                                                               Detroit, Michigan
$40,000,000                                                     January 25, 2001

         On or before the Revolving Credit Maturity Date (which initially is
March 31, 2002), FOR VALUE RECEIVED, NEWCOR, INC., a Delaware corporation
(herein called "Company") promises to pay to the order of COMERICA BANK, a
Michigan banking corporation (herein called "Bank") at its Main Office at 500
Woodward Avenue, Detroit, Michigan, 48226 in lawful money of the United States
of America the indebtedness or so much of the sum of Forty Million Dollars
($40,000,000) as may from time to time have been advanced and then be
outstanding hereunder pursuant to the Third Amended and Restated Revolving
Credit Agreement dated January 15, 1998, made by and between Company and Bank
(as amended from time to time, herein called "Agreement"), together with
interest thereon as hereinafter set forth.

         Each of the Advances made hereunder shall bear interest at the
Eurodollar-based Rate or the Prime-based Rate as elected by Company or as
otherwise determined under the Agreement.

         Interest on the unpaid balance of all Prime-based Advances shall be
payable quarterly commencing on January 31, 2001 and on the last day of each
quarter thereafter. Interest accruing at the Prime-based Rate shall be computed
on the basis of a 360 day year and assessed for the actual number of days
elapsed, and in such computation effect shall be given to any change in the
Prime-based Rate on the date of such change in the Prime-based Rate.

         Interest on each Eurodollar-based Advance shall be payable on the last
day of the Interest Period applicable thereto. Interest accruing at the
Eurodollar-based Rate shall be computed on the basis of a 360 day year and
assessed for the actual number of days elapsed from the first day of the
Interest Period applicable thereto to but not including the last day thereof.

         From and after the occurrence of any event of default hereunder or
under the Agreement or any event which automatically causes the indebtedness
outstanding hereunder to become immediately due and payable, the indebtedness
outstanding hereunder shall bear interest at Three percent (3%) above the
Prime-based Rate as it may vary from time to time, which interest shall be
payable daily.

<PAGE>   6

         This Note is a note under which advances, repayments and readvances may
be made from time to time, subject to the terms and conditions of the Agreement.
This Note evidences borrowing under, is subject to, is secured in accordance
with, and may be matured under, the terms of the Agreement, to which reference
is hereby made. As additional security for this Note, Company grants Bank a lien
on all property and assets including deposits and other credits of the Company,
at any time in possession or control of or owing by Bank for any purpose.

         Company hereby waives presentment for payment, demand, protest and
notice of dishonor and nonpayment of this Note and agrees that no obligation
hereunder shall be discharged by reason of any extension, indulgence, release,
or forbearance granted by any holder of this Note to any party now or hereafter
liable hereon or any present or subsequent owner of any property, real or
personal, which is now or hereafter security for this Note. Any transferees of,
or endorser, guarantor or surety paying this Note in full shall succeed to all
rights of Bank, and Bank shall be under no further responsibility for the
exercise thereof or the loan evidenced hereby. Nothing herein shall limit any
right granted Bank by other instrument or by law.

         This Note is a replacement for a Revolving Credit Note dated January
15, 1998 in the original principal amount of $50,000,000 by Company payable to
Bank.

         All capitalized terms used but not defined herein shall have the
meanings ascribed to them in the Agreement.

                            NEWCOR, INC.

                            By:        /s/ James J. Connor
                               -----------------------------------------------

                            Its:         President & Chief Executive Officer
                               -----------------------------------------------

                            By:          /s/ Thomas D. Parker
                               -----------------------------------------------

                            Its:  Vice-President Human Resources & Secretary
                               -----------------------------------------------

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