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740T/1041 Axle/3.73 G80 - NO DRAIN PLUG? Am I crazy?

Mylesofsmyles

A Member
Joined
Jan 18, 2010
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)
 

white855T

Active member
Joined
Sep 8, 2013
Location
Dallas,TX
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.
 

Mylesofsmyles

A Member
Joined
Jan 18, 2010
Whoa, really.

So I'm effectively breaching that that seal each time I do that though. Almost better off pulling and resealing the cover
 

2manyturbos

Moderator
Joined
Mar 8, 2003
Location
Monroe, OR USA
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.
 

Mylesofsmyles

A Member
Joined
Jan 18, 2010
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.
 

2manyturbos

Moderator
Joined
Mar 8, 2003
Location
Monroe, OR USA
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.
 

Mylesofsmyles

A Member
Joined
Jan 18, 2010
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.
 

white855T

Active member
Joined
Sep 8, 2013
Location
Dallas,TX
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.


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.
 

Mylesofsmyles

A Member
Joined
Jan 18, 2010
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.

:nod:

Invariably my antics will lead me to doing it. It's a matter of when now.
 

dl242gt

Old and boxy but good.
Joined
Jun 21, 2002
Location
S NJ, a suburb of Phila.
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. :lol:
 
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