Rear main seal - install forward or backwards?

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Sep 18, 2011 | 05:02 PM

Rick_Vor

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From: Lafayette, CA

Rear main seal - install forward or backwards?

I've ran into a bunch of posts that recommend installing the new style OEM rear main seal backwards on boosted application.

I put a new OEM rear main seal the recommend way (this side out markings facing out) on my forged 370 when I assembled it. It took quite a few tries to install if so I may have just jacked it up suring the install. It's got a steady drip leak at idle (18" vacuum) so I need to replace it before I put it under any boost. I thought I'd ask before I start dropping my 4L80E and transfer case. It's a solid 8-10 hour job so I'd rather not have to do it again.

By the way, I'm running 5/8" hose from each valve cover to a catch can so I haven't had any issues with a boosted crankcase focing oil out the seal on the original motor.

Also, any preference for OEM or Felpro?

Rick

Sep 18, 2011 | 05:54 PM

FasTimeSS

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From: DFW

Curious

Sep 18, 2011 | 09:06 PM

FMX05

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From: Aiken, SC

I've heard both ways as well. I remember seeing an engine builder say they have better luck installing it backwards. I put mine in as gm intended. So far my 390 hasn't seen any boost but its been in nearly a year with no leaks.

Sep 18, 2011 | 09:23 PM

cleonard

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what about when installing oil pan and front cover at same time.

Sep 18, 2011 | 10:21 PM

BKnBLK05

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From: Glen St Mary,Fla.

Been through this put it in right,make sure it's tap all the way to the bottom of the cover...you shoud be fine

Sep 19, 2011 | 12:29 PM

pwrtrip75

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Quote:

Originally Posted by cleonard

what about when installing oil pan and front cover at same time.

lol..

Sep 19, 2011 | 03:48 PM

cleonard

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Quote:

Originally Posted by pwrtrip75

lol..

jokes on me i guess. what i meant was what is torque sequence when having all of them off.

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Sep 19, 2011 | 03:50 PM

FMX05

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From: Aiken, SC

Quote:

Originally Posted by BKnBLK05

Been through this put it in right,make sure it's tap all the way to the bottom of the cover...you shoud be fine

If I remember correctly this is what gets people. When they do it "by the book" the book is telling them how to install the old seal. I think the old seal had to be installed to a certain depth but not bottomed out. The new one likes to be seated all the way in.

Just be careful not to force it too much. I didn't have a piece of pipe big enough to go that route so I used a small rubber mallet, a block of wood, and my fingers. You should be able to feel when it is evenly seated.