Rear Main Seal

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?

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.

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)

strutaeng said:

The top bellhousing bolts are hard to get to

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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 ?

viven44 said:

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 ?

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

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.

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.

RaiderRodney said:

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.

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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 said:

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.

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To check out the test start,oil leak check;

frank1 said:

To check out the test start,oil leak check;

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

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

Very cool !!