<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2013-03-18</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0000748015</issuerCik>
        <issuerName>SEALY CORP</issuerName>
        <issuerTradingSymbol>ZZ</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001472698</rptOwnerCik>
            <rptOwnerName>KKR Fund Holdings L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O KOHLBERG KRAVIS ROBERTS &amp; CO. L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>9 WEST 57TH STREET, SUITE 4200</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001472697</rptOwnerCik>
            <rptOwnerName>KKR Fund Holdings GP Ltd</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O KOHLBERG KRAVIS ROBERTS &amp; CO. L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>9 WEST 57TH STREET, SUITE 4200</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001472696</rptOwnerCik>
            <rptOwnerName>KKR Group Holdings L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O KOHLBERG KRAVIS ROBERTS &amp; CO. L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>9 WEST 57TH STREET, SUITE 4200</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001472695</rptOwnerCik>
            <rptOwnerName>KKR Group Ltd</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O KOHLBERG KRAVIS ROBERTS &amp; CO. L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>9 WEST 57TH STREET, SUITE 4200</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001404912</rptOwnerCik>
            <rptOwnerName>KKR &amp; Co. L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O KOHLBERG KRAVIS ROBERTS &amp; CO. L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>9 WEST 57TH STREET, SUITE 4200</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001472694</rptOwnerCik>
            <rptOwnerName>KKR Management LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O KOHLBERG KRAVIS ROBERTS &amp; CO. L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>9 WEST 57TH STREET, SUITE 4200</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001081714</rptOwnerCik>
            <rptOwnerName>KRAVIS HENRY R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O KOHLBERG KRAVIS ROBERTS &amp; CO. L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>9 WEST 57TH STREET, SUITE 4200</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001081715</rptOwnerCik>
            <rptOwnerName>ROBERTS GEORGE R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O KOHLBERG KRAVIS ROBERTS &amp; CO. L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>9 WEST 57TH STREET, SUITE 4200</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.01 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2013-03-18</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>46625921</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>2.20</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnotes</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>8% Senior Secured Third Lien Convertible Note due 2016</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2013-03-18</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>4939889.47</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2016-07-15</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $0.01 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>123497237</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnotes</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Shares of common stock, par value $0.01 per share of Sealy Corporation (&quot;Common Stock&quot;) were disposed of in exchange for the right to receive $2.20 per share in cash pursuant to the Agreement and Plan of Merger by and among Tempur-Pedic International Inc., Silver Lightning Merger Company and Sealy Corporation (the &quot;Merger Agreement&quot;).</footnote>
        <footnote id="F2">These 8% Senior Secured Third Lien Convertible Notes due 2016 (the &quot;Convertible Notes&quot;) were co-issued by Sealy Corporation and Sealy Mattress Company and were immediately exercisable upon issuance.  In connection with the merger, the Convertible Notes are no longer convertible into shares of Common Stock and are instead convertible into an amount of cash as calculated pursuant to the terms of the Convertible Notes and the Merger Agreement.</footnote>
        <footnote id="F3">These securities are held by Sealy Holding LLC. Each of KKR Millennium Fund L.P. (as the senior member of Sealy Holding LLC); KKR Associates Millennium L.P. (as the sole general partner of KKR Millennium Fund L.P.); KKR Millennium GP LLC (as the sole general partner of KKR Associates Millennium L.P.); KKR Fund Holdings L.P. (as the designated member of KKR Millennium GP LLC); KKR Fund Holdings GP Limited (as a general partner of KKR Fund Holdings L.P.); KKR Group Holdings L.P. (as a general partner of KKR Fund Holdings L.P. and the sole shareholder of KKR Fund Holdings GP Limited); KKR Group Limited (as the sole general partner of KKR Group Holdings L.P.); KKR &amp; Co. L.P. (as the sole shareholder of KKR Group Limited); and KKR Management LLC (as the sole general partner of KKR &amp; Co. L.P.) may be deemed to have or share beneficial ownership of the securities held by Sealy Holding LLC. KKR Partners III, L.P. is also a member of Sealy Holding LLC.</footnote>
        <footnote id="F4">As the designated members of KKR Management LLC, Henry R. Kravis and George R. Roberts may be deemed to have or share beneficial ownership of the securities held by Sealy Holding LLC. In addition, KKR Fund Holdings L.P. has designated Messrs. Kravis and Roberts as managers of KKR Millennium GP LLC.</footnote>
        <footnote id="F5">Each Reporting Person and each other person named in notes (3) and (4) above disclaims beneficial ownership of any securities reported herein, except to the extent of such person's pecuniary interest therein. The filing of this statement shall not be deemed an admission that, for purposes of Section 16 of the Securities Exchange Act of 1934 or otherwise, the Reporting Persons are the beneficial owners of any equity securities covered by this statement.</footnote>
    </footnotes>

    <remarks>Exhibit 24 Power of Attorney. Because no more than 10 reporting persons can file any one Form 4 through the Securities and Exchange Commission's EDGAR system, Sealy Holding LLC, KKR Millennium Fund L.P., KKR Associates Millennium L.P., and KKR Millennium GP LLC have made a separate Form 4 filing.</remarks>

    <ownerSignature>
        <signatureName>/s/ Richard J. Kreider, Attorney-in-fact for William J. Janetschek, Director, KKR Fund Holdings GP Limited, General Partner for KKR Fund Holdings L.P.</signatureName>
        <signatureDate>2013-03-20</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Richard J. Kreider, Attorney-in-fact for William J. Janetschek, Director for KKR Fund Holdings GP Limited</signatureName>
        <signatureDate>2013-03-20</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Richard J. Kreider, Attorney-in-fact for William J. Janetschek, Director, KKR Group Limited, General Partner for KKR Group Holdings L.P.</signatureName>
        <signatureDate>2013-03-20</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Richard J. Kreider, Attorney-in-fact for William J. Janetschek, Director for KKR Group Limited</signatureName>
        <signatureDate>2013-03-20</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Richard J. Kreider, Attorney-in-fact for William J. Janetschek, Chief Financial Officer, KKR Management LLC, General Partner for KKR &amp; Co. L.P.</signatureName>
        <signatureDate>2013-03-20</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Richard J. Kreider, Attorney-in-fact for William J. Janetschek, Chief Financial Officer for KKR Management LLC</signatureName>
        <signatureDate>2013-03-20</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Richard J. Kreider, Attorney-in-fact for Henry R. Kravis</signatureName>
        <signatureDate>2013-03-20</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Richard J. Kreider, Attorney-in-fact for George R. Roberts</signatureName>
        <signatureDate>2013-03-20</signatureDate>
    </ownerSignature>
</ownershipDocument>
