Exhibit 10(a)(1)
 [*] TEXT OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION
Confidential Treatment Requested by Core Molding Technologies, Inc.
Under 17 C.F.R. Sections 200.80(B)(4), 200.83 and 240.24b-2
 FIRST ADDENDUM TO COMPREHENSIVE SUPPLY AGREEMENT
 THIS FIRST ADDENDUM CORE MOLDING TECHNOLOGIES, INC./CORE COMPOSITES
CORPORATION
 WHEREAS,
 WHEREAS,
 NOW, THEREFORE,
 1.
    
    Seller will install, at its expense (approximately $4,000,000), additional compression
molding presses at its plant in Matamoros, Mexico, in numbers and configurations needed to
ensure adequate capacity to produce the following Products under historically-typical
demand conditions:
 a.
    
    [*]
 b.
    
    [*]
 c.
    
    [*]
 d.
    
    [*]
 2.
    
    [*]
 [*]
    
    [*]
    
    [*]
    
    [*]
    
    [*][*]
    
    [*]
    
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    [*]  *[*]
    
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    [*]  *[*]
    
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    [*][*]
    
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    [*]  *[*]
    
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    [*]  *[*]
    
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    [*]  *[*]
    
    [*]
    
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    [*]  *
  * Confidential Treatment Requested by Core Molding Technologies, Inc




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3.
    
    Seller and Buyer will develop a final move timeline once the inventory bank sizes are
determined, as the size of the bank will impact timing. It is currently estimated that
production start-up for the [*] will start in Mexico in May 2010 and production of the [*]
will begin in June 2010.
 4.
    
    Seller will initiate move of production lines to Mexico once this First Addendum is
executed and the inventory bank sizes are determined.
 5.
    
    Buyer will be responsible for all costs as noted in the cost breakdown of the attached
Appendix A,
of the inventory bank. Final costs will be determined based upon the actual bank quantities
determined to be necessary.
 a.
    
    Buyer may at its own option choose to purchase and store the bank at
Buyers (or its logistics vendors) facility. Should Buyer chose to store the bank,
Buyer will be responsible to ensure that all Products are properly stored to avoid
any damage during storage and to ensure products remain in a paint-ready condition
for use by Buyers production facilities.
 6.
    
    Buyer will be responsible for the costs of moving its molds, secondary equipment,
racks, etc., as shown in the cost breakdown in the attached Appendix A, to Sellers
Matamoros Mexico plant.
 a.
    
    Buyer may contract directly with its logistic suppliers to transport
these items to Mexico. Seller will support the loading and unloading of these
items in its facilities. Buyer and Seller will work together to ensure that the
timing of these moves is in support of the overall project timeline and start up
needs.
 b.
    
    Alternatively, if directed by Buyer, Seller will contract with the
logistics carriers to transport these items to Mexico. Under this arrangement,
Seller will bill Buyer for the costs to move this equipment. Payment terms will
match those Seller receives from the logistics carriers.
 7.
    
    Buyer will be responsible for the costs to disconnect, transfer and reinstall in
Sellers Matamoros plant, all Buyer-owned assembly cell equipment. These costs are shown
in the cost breakdown in the attached Appendix A. Seller will be responsible to manage
this transfer to ensure that all equipment is properly disassembled and reassembled to
produce Products consistent with the assembly of these Products in Columbus.
 a.
    
    [*]
 b.
    
    [*].
 c.
    
    Seller will invoice Buyer progress billings consistent with service
vendors invoicing practices.
 d.
    
    Payment terms for these invoices from Seller to Buyer will match the
providers invoice payment terms.
 * Confidential Treatment Requested by Core Molding Technologies, Inc




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8.
    
    The parties recognize that, should production using the Products covered by this First
Addendum be moved from Buyers Escobedo plant to any other location further from Sellers
Matamoros Plant than the Escobedo Assembly Plant, Buyer will experience higher logistics
costs for its products shipped from Sellers Matamoros facility. Buyer agrees not use
logistics costs as a basis to deem Seller uncompetitive as a supplier under section 19 of
the Supply Agreement, should such a move occur.
 9.
    
    All other terms and conditions of the Supply Agreement shall remain in full force and
effect.
 CORE MOLDING TECHNOLOGIES, INC.
    
    
    
    NAVISTAR, INC./s/ Terrence J. ODonovan
    
    
    
    /s/ Dustin J. MillerTerrence J. ODonovan, VP
    
    
    
    Dustin J. Miller, Supply ManagerJanuary 28, 2010
    
    
    
    January 28, 2010Date
    
    
    
    Date
 * Confidential Treatment Requested by Core Molding Technologies, Inc




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[*] TEXT OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION
Confidential Treatment Requested by Core Molding Technologies, Inc.
Under 17 C.F.R. Sections 200.80(B)(4), 200.83 and 240.24b-2
  * Confidential Treatment Requested by Core Molding Technologies, Inc