Head Gasket Fits John Deere 4020 600 4010 6404D R45615One New Aftermarket Replacement Head Gasket Fits John Deere 4010, 4020, 4000, and 600 Tractors This aftermarket replacement cylinder head gasket Fits John Deere tractors and industrial construction equipment equipped with the 6. 404D six cylinder diesel engine. It seals the cylinder head to the engine block, maintaining compression and preventing coolant or oil from entering the combustion chamber. Compatible with early serial number machines (s n