-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 J2I/m6ZuSLbOpDl/PEwx3OcPIAZRYWq3Acn/Q7T7Plrtf6LdxRbyIEM1dwhEScAX
 ynkIQWIz4qV7H/kCimvkGQ==

<SEC-DOCUMENT>0001223464-10-000002.txt : 20100308
<SEC-HEADER>0001223464-10-000002.hdr.sgml : 20100308
<ACCEPTANCE-DATETIME>20100308133242
ACCESSION NUMBER:		0001223464-10-000002
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20100306
FILED AS OF DATE:		20100308
DATE AS OF CHANGE:		20100308

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			KAHLER JOHN S
		CENTRAL INDEX KEY:			0001223464

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-21835
		FILM NUMBER:		10663049

	MAIL ADDRESS:	
		STREET 1:		1500 WEST UNIVERSITY PARKWAY
		CITY:			SARASOTA
		STATE:			FL
		ZIP:			34243

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			SUN HYDRAULICS CORP
		CENTRAL INDEX KEY:			0001024795
		STANDARD INDUSTRIAL CLASSIFICATION:	MISCELLANEOUS FABRICATED METAL PRODUCTS [3490]
		IRS NUMBER:				592754337
		STATE OF INCORPORATION:			FL
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1500 WEST UNIVERSITY PKWY
		CITY:			SARASOTA
		STATE:			FL
		ZIP:			34243
		BUSINESS PHONE:		9413621200

	MAIL ADDRESS:	
		STREET 1:		1500 WEST UNIVERSITY PKWY
		CITY:			SARASOTA
		STATE:			FL
		ZIP:			34243
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-03-06</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001024795</issuerCik>
        <issuerName>SUN HYDRAULICS CORP</issuerName>
        <issuerTradingSymbol>SNHY</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001223464</rptOwnerCik>
            <rptOwnerName>KAHLER JOHN S</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1500 WEST UNIVERSITY PARKWAY</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SARASOTA</rptOwnerCity>
            <rptOwnerState>FL</rptOwnerState>
            <rptOwnerZipCode>34243</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2010-03-06</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>313</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>26.16</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>313</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5007.68</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Stock Units issued and held for the account of the reporting person under the Amended and Restated 2004 Nonemployee Director Equity and Deferred Compensation Plan.  In connection with any distribution to the reporting person under the Plan, Stock Units are payable in shares of common stock on a 1 for 1 basis.  The reporting person is fully vested in all Stock Units issued to him and held for his account, and there is no expiration date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Gregory C. Yadley, as Attorney-in-Fact for JOHN S. KAHLER</signatureName>
        <signatureDate>2010-03-08</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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