-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 IWGscHDITyeGUnwZnyXsxkXer7g6/H2mERM4ZhSy3I+3t0T8/3mC/IoK7j1YsbHr
 Yf3c2mQkByyf4OF960+1Ag==

<SEC-DOCUMENT>0000938885-03-000007.txt : 20030804
<SEC-HEADER>0000938885-03-000007.hdr.sgml : 20030804
<ACCEPTANCE-DATETIME>20030804194343
ACCESSION NUMBER:		0000938885-03-000007
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030801
FILED AS OF DATE:		20030804

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			ROGERS JOHN W JR
		CENTRAL INDEX KEY:			0000938885

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-02328
		FILM NUMBER:		03821934

	BUSINESS ADDRESS:	
		STREET 1:		ARIEL CAPITAL MANAGEMENT, INC.
		STREET 2:		200 EAST RANDOLPH DRIVE, SUITE 2900
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60601

	MAIL ADDRESS:	
		STREET 1:		ARIEL CAPITAL MANAGEMENT, INC.
		STREET 2:		200 EAST RANDOLPH DRIVE, SUITE 2900
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60601

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			GATX CORP
		CENTRAL INDEX KEY:			0000040211
		STANDARD INDUSTRIAL CLASSIFICATION:	TRANSPORTATION SERVICES [4700]
		IRS NUMBER:				361124040
		STATE OF INCORPORATION:			NY
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		500 W MONROE  ST
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60661
		BUSINESS PHONE:		3126216200

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	GENERAL AMERICAN TRANSPORTATION CORP
		DATE OF NAME CHANGE:	19750722
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc4.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>
    <periodOfReport>2003-08-01</periodOfReport>
    <notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000040211</issuerCik>
        <issuerName>GATX CORP</issuerName>
        <issuerTradingSymbol>GMT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000938885</rptOwnerCik>
            <rptOwnerName>ROGERS JOHN W JR</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ARIEL CAPITAL MANAGEMENT, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>200 EAST RANDOLPH DRIVE, SUITE 2900</rptOwnerStreet2>
            <rptOwnerCity>CHICAGO</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60601</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>
  <nonDerivativeTable>
   <nonDerivativeTransaction>
      <securityTitle>
          <value>Common Stock</value>
      </securityTitle>
      <transactionDate>
          <value>2003-08-01</value>
      </transactionDate>
      <transactionCoding>
          <transactionFormType>4</transactionFormType>
          <transactionCode>A</transactionCode>
          <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
      <value />
      </transactionTimeliness>
      <transactionAmounts>
          <transactionShares>
              <value>1000.45</value>
              <footnoteId id="F1" />
          </transactionShares>
          <transactionPricePerShare>
              <value>22.24</value>
          </transactionPricePerShare>
          <transactionAcquiredDisposedCode>
              <value>A</value>
          </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
          <sharesOwnedFollowingTransaction>
              <value>10512.43</value>
              <footnoteId id="F2" />
          </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
          <directOrIndirectOwnership>
              <value>D</value>
          </directOrIndirectOwnership>
      </ownershipNature>
   </nonDerivativeTransaction>
  </nonDerivativeTable>
  <derivativeTable>
  </derivativeTable>
<footnotes>
   <footnote id="F1">Includes that portion of (a) the quarterly payment of the annual directors' fee (640.7374 shares) credited to an account established for each director under the GATX Directors' Phantom Stock Plan ("Phantom Stock Plan") and (b) the annual retainer and meeting fee (359.7122 shares) which the reporting person elected to invest in units of phantom stock under the Directors' Deferred Fee Plan which in each case will be settled in common stock upon the expiration of the director's service on the Board. </footnote>
   <footnote id="F2">Includes 116.1089 shares acquired pursuant to a dividend reinvestment feature of the Phantom Stock Plan and 37.2125 shares acquir
ed pursuant to a dividend reinvestment feature of the Deferred Fee Plan.</footnote>
</footnotes>
    <ownerSignature>
       <signatureName>John W. Rogers, Jr.</signatureName>
       <signatureDate>2003-08-01</signatureDate>
    </ownerSignature>
    <ownerSignature>
       <signatureName>Lisa M. Ibarra, by Power of Attorney on behalf of John W. Ro</signatureName>
       <signatureDate>2003-08-01</signatureDate>
    </ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----
