Rear main seal

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

latvius

Full Access Member
Joined
Nov 17, 2014
Posts
432
Reaction score
600
Location
Ariton Alabama
That's not an alignment tool. It's just to keep the seal surface intact. The alignment tool is usually aluminum. You remove the old seal and then when reinstalling the cover, place the tool in where the seal would go. Bolt everything in place and torque. Then you install the seal last.
Yeah it is an alignment tool, just not a great one. Below is how Felpro describes the seal

1724159066185.png
 

drdave81

Full Access Member
Joined
Oct 7, 2020
Posts
239
Reaction score
366
Location
Waterford, MI
I didn't realize there would be that much wiggle room on all the bolts. Do you have to do the same thing with the front too?
There are alignment tools for the front and rear covers. If the oil pan is off, you need to align the covers both up and down, as well as side to side. If the pan is still on, then they only need to be aligned side to side. I've never used one for the front cover, as I have an old harmonic balancer that I took a grinder to the inside of so it will fit snuggly, but slip on and off. That's my alignment tool. Since the covers can move side to side, you can have excessive pressure on one side of the seal, and a lack of pressure, causing it to sit incorrectly and leak.
I've never had to align the rear cover, since if it's not leaking, I'm not messing with it lol.
 

89Suburban

Bull in the china shop
Supporting Member
Joined
Jan 10, 2013
Posts
15,085
Reaction score
41,748
Location
SE PA
There are alignment tools for the front and rear covers. If the oil pan is off, you need to align the covers both up and down, as well as side to side. If the pan is still on, then they only need to be aligned side to side. I've never used one for the front cover, as I have an old harmonic balancer that I took a grinder to the inside of so it will fit snuggly, but slip on and off. That's my alignment tool. Since the covers can move side to side, you can have excessive pressure on one side of the seal, and a lack of pressure, causing it to sit incorrectly and leak.
I've never had to align the rear cover, since if it's not leaking, I'm not messing with it lol.


Wow good to know, appreciate it.
 

latvius

Full Access Member
Joined
Nov 17, 2014
Posts
432
Reaction score
600
Location
Ariton Alabama
There are alignment tools for the front and rear covers. If the oil pan is off, you need to align the covers both up and down, as well as side to side. If the pan is still on, then they only need to be aligned side to side. I've never used one for the front cover, as I have an old harmonic balancer that I took a grinder to the inside of so it will fit snuggly, but slip on and off. That's my alignment tool. Since the covers can move side to side, you can have excessive pressure on one side of the seal, and a lack of pressure, causing it to sit incorrectly and leak.
I've never had to align the rear cover, since if it's not leaking, I'm not messing with it lol.
" If the oil pan is off, you need to align the covers both up and down, as well as side to side. If the pan is still on, then they only need to be aligned side to side."

This makes no sense to me, the alignment tool puts the cover equal distance around the crankshaft, you're not going to be moving the cover side to side. You could rotate it a bit but once you have all the bolts in it would be very minimal.
Have you used an alignment tool to install the rear main?
 

drdave81

Full Access Member
Joined
Oct 7, 2020
Posts
239
Reaction score
366
Location
Waterford, MI
" If the oil pan is off, you need to align the covers both up and down, as well as side to side. If the pan is still on, then they only need to be aligned side to side."

This makes no sense to me, the alignment tool puts the cover equal distance around the crankshaft, you're not going to be moving the cover side to side. You could rotate it a bit but once you have all the bolts in it would be very minimal.
Have you used an alignment tool to install the rear main?
Right, I meant without the alignment tool, the cover can move side to side and have the seal sitting offset left or right.

And yes that video shows him keeping the plastic piece in there, but if it basically falls off, how well is it really aligning anything? If it worked for him, cool though. There's also people who have installed covers without any tool and not had a leak. I'd also not advise that, but it's been done. People reuse TTY head bolts and are fine........ It comes down more to a luck of the draw.

Then there's people who don't do things the correct way and have issues.
 

strutaeng

Full Access Member
Joined
Aug 10, 2023
Posts
1,178
Reaction score
2,444
Location
Dallas, Texas
I did the rear main seal like 3 years ago on my 06 Suburban. I bought the Sac City tool. I followed the instructions centering the cover, then installed the crank flange seal. Torqued everything.

Then when I got back to my workbench, there was the cover gasket! LMAO

So I had to remove the cover and reinstall it, which kinda negated the centering tool because I had already installed the round seal. I just torqued the 2 smaller long bolts to the same specs, which was like 108 in-lbs IIRC.

This spring I refreshrened the engine due to a lifter tick. I reused the rear main seal and I installed it again like that.
 

Forum statistics

Threads
132,307
Posts
1,865,717
Members
96,896
Latest member
grass209
Top