i didnt replace the chain tensioner seal.so far no leaks.overall the job went fairly fast.say 2 hrs each way for the Rand R.be very careful whilst unbolting the cam and scratch mark the cam gear and chain so you can reset to the original timing.definately recommend staying cool calm and collected during the proceedure.so any tasty liquid libation will definately be helpful

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michael cole 1980 300SD gone now but not forgotten,87tdt,90 300te 4matic 95 e320 wagon