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Old 11-13-2022, 09:38 PM   #1
Mylesofsmyles
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Default 740T/1041 Axle/3.73 G80 - NO DRAIN PLUG? Am I crazy?

So I've been looking at my differential for considerably longer than anticipated, or am I comfortable admitting, and I can't find the darn drain plug.

I see the fill plug, even topped it off before driving the car home. But where's the drain. I've looked in obvious places on the cast housing, and see nothing.

Were there batches of these without drains? Did Volvo expect us to remove the cover? Vacuum pump?

For reference, it's a 1992 Volvo 740 Turbo Wagon. (10/91 manufacturing date)
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Old 11-13-2022, 10:08 PM   #2
hessam69
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Remove the lowest bolt from the cover. It will allow the oil to drain out
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Old 11-13-2022, 10:51 PM   #3
white855T
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Yeah, the lowest bolt is the drain. It won't completely drain but its good enough. Your diff cover doesn't use a gasket but a sealant.
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Old 11-14-2022, 01:39 AM   #4
Mylesofsmyles
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Whoa, really.

So I'm effectively breaching that that seal each time I do that though. Almost better off pulling and resealing the cover
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Old 11-14-2022, 02:19 AM   #5
2manyturbos
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Quote:
Originally Posted by Mylesofsmyles View Post
Whoa, really.

So I'm effectively breaching that that seal each time I do that though. Almost better off pulling and resealing the cover
No, you're not. Just pull the bolt and let it drain. Put a small dab of sealant on the seating surface of the bolt head when you reinstall it after cleaning the oil off the cover and bolt hole.
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Old 11-14-2022, 12:53 PM   #6
Mylesofsmyles
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No, you're not. Just pull the bolt and let it drain. Put a small dab of sealant on the seating surface of the bolt head when you reinstall it after cleaning the oil off the cover and bolt hole.
Fair enough for intervals. Considering I just dragged this greasy mess home wit over 460k on ODO, I'm thinking it wise to reseal the cover now. Then maybe try your trick annually with routine fluids flushes.
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Old 11-14-2022, 03:06 PM   #7
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Fair enough for intervals. Considering I just dragged this greasy mess home wit over 460k on ODO, I'm thinking it wise to reseal the cover now. Then maybe try your trick annually with routine fluids flushes.
I have never seen one of the aluminum covers leak if they haven't been tampered with. It's a stiff casting that is machined flat and sealed with a thin layer of silicon based sealant. Just like an airplane engine. No gasket that can shrink/crack/compress. If you pop it off there you have a lot of work ahead of you cleaning up the surfaces.
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Old 11-14-2022, 03:13 PM   #8
Mylesofsmyles
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I have never seen one of the aluminum covers leak if they haven't been tampered with. It's a stiff casting that is machined flat and sealed with a thin layer of silicon based sealant. Just like an airplane engine. No gasket that can shrink/crack/compress. If you pop it off there you have a lot of work ahead of you cleaning up the surfaces.
This sounds like the old "if it ain't broke" logic, and I'm following along. I will trust this and give it a go.

Thanks for talking me through all this nonsense.
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Old 11-14-2022, 03:52 PM   #9
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Quote:
Originally Posted by 2manyturbos View Post
I have never seen one of the aluminum covers leak if they haven't been tampered with. It's a stiff casting that is machined flat and sealed with a thin layer of silicon based sealant. Just like an airplane engine. No gasket that can shrink/crack/compress. If you pop it off there you have a lot of work ahead of you cleaning up the surfaces.
To pop off cover and clean it/paint is a few hours of work. Op is already in the process of refurbusing his car. It wouldn't be a lot of extra work.


Quote:
Originally Posted by Mylesofsmyles View Post
This sounds like the old "if it ain't broke" logic, and I'm following along. I will trust this and give it a go.

Thanks for talking me through all this nonsense.
It wouldn't be any more extra work than what you're already doing.
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Old 11-14-2022, 04:43 PM   #10
Mylesofsmyles
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To pop off cover and clean it/paint is a few hours of work. Op is already in the process of refurbusing his car. It wouldn't be a lot of extra work.

It wouldn't be any more extra work than what you're already doing.


Invariably my antics will lead me to doing it. It's a matter of when now.
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Old 11-16-2022, 07:02 PM   #11
dl242gt
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Plus when you pry off the cover you will be pulling on the wiring for the speed sensor which will invariably crack and probably break while futzing with the cover removal.
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