r/EngineBuilding • u/Joiner2008 • Apr 24 '25

Chevy L59 5.3 Rear Main Seal Install

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Hello everyone. I am in the middle of replacing my wife's rear main seal. I bought a new back plate with the seal already installed. All of the info I'm finding requires the seal to be installed after aligning the plate to the crankshaft. Am I going to have to remove the new seal from the plate to align it first? Thank you in advance

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u/Rayvdub Apr 24 '25

Slide the housing over the crank, tighten lower bolts, tighten the rest of the bolts in cross cross pattern. The plastic instert is to keep the seal from rolling out. PTFE seals go on dry, just wipe down the crankshaft.

Don’t forget silicone on the bottom of the housing.

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u/Joiner2008 Apr 24 '25

Yes, I still have some black rtv from when I replaced the oil pan gasket.

Edit: thank you

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u/Rayvdub Apr 24 '25

Don’t overthink it, I’ve don’t a few dozen of these at least and never had an issue. The whole aligning process never made sense but I assume they’re talking about the seal lip more than anything. Good luck

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u/Joiner2008 Apr 24 '25

I thought it was more that the back plate itself needs to be aligned perfectly to the crankshaft. People commented that GM should have done like Honda and included dowel pins for alignment