Rear main seal

[Peeledpeas]

I just replaced my rear main seal while I was swapping the transmission a couple months ago but it appears to be leaking already. Is there anything else that could leak that might look like a rear main leak? I can definitely see a stream of oil comin down behind the flex plate. I'm pretty sure I got a good look at the oil pressure sensor and it doesn't appear to be leaking. Kinda really annoyed about this. Was a Felpro seal set with cover gasket and I followed the instructions. 2005 GMC Yukon 5.3L

 

[mountie]

I just replaced my rear main seal while I was swapping the transmission a couple months ago but it appears to be leaking already. Is there anything else that could leak that might look like a rear main leak? I can definitely see a stream of oil comin down behind the flex plate. I'm pretty sure I got a good look at the oil pressure sensor and it doesn't appear to be leaking. Kinda really annoyed about this. Was a Felpro seal set with cover gasket and I followed the instructions. 2005 GMC Yukon 5.3L

Ouch...... Something failed...... Get it on a lift..... clean the area good..... maybe you'll find it?
Sorry to hear, you might have to do it all again..... Bummer....

 

[justirv]

I just replaced my rear main seal while I was swapping the transmission a couple months ago but it appears to be leaking already. Is there anything else that could leak that might look like a rear main leak? I can definitely see a stream of oil comin down behind the flex plate. I'm pretty sure I got a good look at the oil pressure sensor and it doesn't appear to be leaking. Kinda really annoyed about this. Was a Felpro seal set with cover gasket and I followed the instructions. 2005 GMC Yukon 5.3L

Installation of a LS rear main seal can be problematic. Did you use any type of alignment or installation tool? Something like the Sac City tool, which will align the cover and seal to the block. If you find this (rear seal) is the problem, I highly recommend one. Good luck.

 

[drdave81]

Yep, if you didn't use the alignment tool, the trans is likely coming back out. Gonna have to redo it unfortunately.

 

[Peeledpeas]

Installation of a LS rear main seal can be problematic. Did you use any type of alignment or installation tool? Something like the Sac City tool, which will align the cover and seal to the block. If you find this (rear seal) is the problem, I highly recommend one. Good luck.

I was unaware of needing an alignment tool. There was a round plastic thing that came in the Felpro set but I take that may have been inadequate for the task?

 

[Peeledpeas]

Yep, if you didn't use the alignment tool, the trans is likely coming back out. Gonna have to redo it unfortunately.

I did it on jack stands last time. I'm hitting up my buddy that has a lift this time. That was a major PITA.

 

[OR VietVet]

Sorry to hear about this. The alignment tool is slick. If you have a lift, unbolt and shift transmission back and suspend it in some way or use adjustable tall stands.

 

[drdave81]

I was unaware of needing an alignment tool. There was a round plastic thing that came in the Felpro set but I take that may have been inadequate for the task?

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.

 

[89Suburban]

I never heard of this alignment tool for the rear main. Is this all LS motors?

 

[latvius]

LS Rear Main and Timing cover AlignIt Tools

Must have tool for aligning the rear main and timing cover on the GM Gen III & IV LS based engines to eliminate premature seal leaks.

www.saccitycorvette.com

 

[latvius]

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

 

[drdave81]

Yeah it is an alignment tool, just not a great one. Below is how Felpro describes the seal

View attachment 435744

The piece just sits inside the seal, there's no way it can align the cover. As you install it, the sleeve is pushed out, but the cover can still move.

 

[drdave81]

I never heard of this alignment tool for the rear main. Is this all LS motors?

Yes it is.

 

[89Suburban]

Yes it is.

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?

 

[drdave81]

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]

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]

The piece just sits inside the seal, there's no way it can align the cover. As you install it, the sleeve is pushed out, but the cover can still move.

Watch this video of a guy who does what you say can't be done.

And NO I am not advocating using it, I bought alignit tools.

 

[latvius]

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]

" 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]

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.