Rear Main Seal

[diezelraccoon]

Well something I have been dreading was the problem is the problem. My 03 Tahoe 2WD with the 5.3 has been leaking some drips of oil and discovered the rear main seal needs to be replaced. I love doing my own work but I just am not sure I have the skill set for this. I know the transmission needs to come out and I’ve never done that before and not sure if I even I have the right tools. I have a lot of tools but that just seems like a pretty heavy job. I’m usually pretty confident doing things but this not so much. I would love to achieve it especially to save money but not sure I can.

Is it really that hard?

 

[strutaeng]

It's not that hard, but does take some grunt. I highly recommend a transmission jack and a helper.

The top bellhousing bolts are hard to get to. You can support the transmission with the jack, remove the crossmember, then slowly and carefully lower the tail shaft. Using some super long extensions (24"), you reach the top bellhousing bolts.

For reinstall of the rear main seal, I recommend you get the centering tool. I have the one by Sac City, but I think the others work just as well. I add a thin layer of permatex aviation sealant before installing it, but I don't think that's necessary. Torque the cover bolts to spec.

 

[viven44]

I haven't done this job on this platform but maybe some general comments

First... @strutaeng mentioned, having a good transmission jack.. I love the Horrid Fate (as some call it, haha) 450 lb manual transmission jack so much that anytime one of those come up (used once or twice) on Facebook marketplace for $50 or so,I grab it... They have so much utility. Nice to have about 2 of these suckers for a transmission....

Second... you lucked out already because you are doing this job on 1) 2WD, and 2) GM ... both factors make this a lot easier

I think the GM torque converters use thread-in bolts vs. studs which makes it easier to get things lined up. Maybe a good opportunity also to consider torque converter if you have any sort of woes (lock up clutch, transmission temp high ?). If you do a lot of city driving, maybe a low-stall converter ?

Since centering is mentioned, I assumed this is because the seal is held by a plate and before you torque the plate bolts you want to make sure the rear main seal is centered durig install ? (Same in principle to some front timing cover seals, or pinion seal in rear ends)

 

[viven44]

The top bellhousing bolts are hard to get to

I usually get the top bellhousing bolts on my other trucks from the engine bay with a flex head ratchet... is that an option here ?

 

[strutaeng]

I usually get the top bellhousing bolts on my other trucks from the engine bay with a flex head ratchet... is that an option here ?

Yes, that's definitely another option, but you really need to remove the intake (easy enough though) to get them through there.

 

[frank1]

I just finished the RM seal and oil pan gasket, with new oil pan, on my plow truck. It's a 02 silverado 2500hd 4x4. I bought the seal installation tool kit, worth the money, for the install, I also had to replace the flex plate and TC, as it was bent and converter had a messes up centering hub. If you need some info, dm me.

 

[RaiderRodney]

I may get some flack for this but have you tried using some ATP-205 re-seal? This stuff can do miracles on rear main seals.

 

[viven44]

I may get some flack for this but have you tried using some ATP-205 re-seal? This stuff can do miracles on rear main seals.

Worth a try.. also begs the question on how bad the leak is and how often is an oil top off needed. Even high mileage oil can reduce the leak possibly.

I am so used to my old trucks needing a top off every 500 miles that if a top off is only needed every 1000 miles, I would not bother with any sort of trouble trying to fix it... I usually find something else to break

 

[frank1]

I just finished the RM seal and oil pan gasket, with new oil pan, on my plow truck. It's a 02 silverado 2500hd 4x4. I bought the seal installation tool kit, worth the money, for the install, I also had to replace the flex plate and TC, as it was bent and converter had a messes up centering hub. If you need some info, dm me.

To check out the test start,oil leak check;

https://www.facebook.com/video.php?v=1048010796990251

 

[viven44]

To check out the test start,oil leak check;

https://www.facebook.com/video.php?v=1048010796990251

What can the GM trucks do that the Fords cannot? Fire up the engine without a transmission!!

Very cool !!

 

[DRLexpress]

I saw in the video one white jumper wire in what I guess is a plug off the transmission. My guess is telling the ECU it is in park. Is that the only thing you have to do to run it like that. No need now but good info to put in the back of my brain.

 

[frank1]

I saw in the video one white jumper wire in what I guess is a plug off the transmission. My guess is telling the ECU it is in park. Is that the only thing you have to do to run it like that. No need now but good info to put in the back of my brain.

Yes, just bypass the neutral safety switch.

 

[West 1]

The Rear Main Seal in the LS style engines is a Teflon Rear Main seal. These can last a million miles with no leak. The LS rear main leaks are usually the rear main plate gasket not the rear main seal.
Since these are Teflon it is necessary to install the seal DRY and CLEAN on a Clean and Dry crankshaft. This allows the teflon to impregnate into he crankshaft and you end up with a perfect seal for the life of the engine. These seals are fantastic but easy to damage on install. Fel Pro or National seals will come with a plastic seal installation tool. You slip the plastic tool over the crankshaft and press in the seal with the plastic protecting it from damage. Once installed you grab the plastic tool and pull it out. I use vise grips to grab it and pull it out. IF the bolts on the cover plate are a little loose the plate should self center to the crankshaft from the pressure of the seal on the crank. Gently torque the cover plate bolts to spec and you should be good to go. National Made these seals and supplies all of Fel Pro seals. National had the GM contract years ago but I have no idea who supplies the GM seal today. Teflon seals were first introduced on Diesel engines in the 1990's and later they were introduced on automotive engines. They are the very best when installed properly.

The biggest change on install is Clean and Dry on the sealing surface. All other types of seals need lubrication not the teflon, lubing teflon can cause leaks. The outside of the seal where it installs into the cover plate has a rubber or type of rubber seal to seal the outside/non rotating part of the seal to the cover plate. To ease this installation a thin film of lubricant/oil can be used to help reduce install effort but Zero oil on the teflon surface where the crank rotates.

If you think I am wrong on this look up Cummins, Detroit Diesel, Caterpillar, or John Deere Teflon Seal installation instructions. They have been using the technology much longer than GM.

Sad part for me, I just did the Oil pan and front main seal a week ago and now find my rear main seal is leaking also. DANG. More work to do. I hate leaks.

 

[S33k3r]

You might want to wait on the rear main seal if it is not leaking a lot.

 

[West 1]

I have the tranny and transfer case out already, will start going back in tomorrow. The leak at the rear main seal plate was obvious. It may be next week before I have time to get it finished. Waiting for some parts to come in, going to do the tranny fluid and filter as long as I am in there. It is a ton of work to drop the tranny for this job. The upper tranny bell housing bolts are difficult. I am thinking of pulling off the manifold for access from the top. I got them out but not sure I will be able to get them back in properly from below.

 

[89Suburban]

What harness is that white wire bypassing? Good stuff.

 

[89Suburban]

Ooops I am late to the party here, sorry.

 

[S33k3r]

I have the tranny and transfer case out already, will start going back in tomorrow. The leak at the rear main seal plate was obvious. It may be next week before I have time to get it finished. Waiting for some parts to come in, going to do the tranny fluid and filter as long as I am in there. It is a ton of work to drop the tranny for this job. The upper tranny bell housing bolts are difficult. I am thinking of pulling off the manifold for access from the top. I got them out but not sure I will be able to get them back in properly from below.

I don't know how far in you are -- or if you've already done this and I have forgotten (sorry) -- but you might want to drop the oil pan, replace it's seal, replace the pickup tube and O-ring, and maybe even the oil pump.

 

[West 1]

About 2 weeks ahead of you on the Oring and Oil Pan. I did the oil pan first thinking that was the main leak. It was leaking but so was my rear main seal gasket at the plate. When I had the oil pan off I also pulled the water pump and timing cover so I could install both a new Oring on the pickup and also I installed the higher pressure spring inside the oil pump. With the higher pressure spring now in the pump I have 65 psi at hot idle and 75 psi hot above 1500 RPM. Previously I had 30 psi hot idle oil pressure and 40+ on the highway.

One unexpected bonus on the higher oil pressure. Since I owned this truck, 11 years now it has had the light knock on start up if you let the truck sit a few days. It would start quiet and a few seconds later develop a light knock which would last for maybe 30 seconds and go away. If you drove it every day this would never happen, only when it sat at least 2 days. That morning knock is GONE. Bonus of having higher oil pressure I guess.

I have new Rod and Main bearings, I almost installed them when I had the oil pan off. Very glad I did not do that, would have been a lot of work for no gain.

With the tranny out for the new rear main seal and plate gasket I went ahead and installed a new barbell. Only because I was there. Did not want to do all this work and not address the barbell.
I won't have time to re install the tranny for a few days. The tranny fluid was a little burned which surprised me as it only has 30,000 miles on it. I do tow a lot and sometimes tow as much as 7,000 pounds so it will get a new tranny filter and fluid also.

Installed the new rear main seal and barbell today so that is ready to go.

 

[S33k3r]

About 2 weeks ahead of you on the Oring and Oil Pan. I did the oil pan first thinking that was the main leak. It was leaking but so was my rear main seal gasket at the plate. When I had the oil pan off I also pulled the water pump and timing cover so I could install both a new Oring on the pickup and also I installed the higher pressure spring inside the oil pump. With the higher pressure spring now in the pump I have 65 psi at hot idle and 75 psi hot above 1500 RPM. Previously I had 30 psi hot idle oil pressure and 40+ on the highway.

One unexpected bonus on the higher oil pressure. Since I owned this truck, 11 years now it has had the light knock on start up if you let the truck sit a few days. It would start quiet and a few seconds later develop a light knock which would last for maybe 30 seconds and go away. If you drove it every day this would never happen, only when it sat at least 2 days. That morning knock is GONE. Bonus of having higher oil pressure I guess.

I have new Rod and Main bearings, I almost installed them when I had the oil pan off. Very glad I did not do that, would have been a lot of work for no gain.

With the tranny out for the new rear main seal and plate gasket I went ahead and installed a new barbell. Only because I was there. Did not want to do all this work and not address the barbell.
I won't have time to re install the tranny for a few days. The tranny fluid was a little burned which surprised me as it only has 30,000 miles on it. I do tow a lot and sometimes tow as much as 7,000 pounds so it will get a new tranny filter and fluid also.

Installed the new rear main seal and barbell today so that is ready to go.

May I suggest adding a heavier duty transmission cooler?