differential vent question - Ford Mustang Forum
 
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post #1 of 10 (permalink) Old 12-21-2015 Thread Starter
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differential vent question

differential vent question - 2013 gt 3.73 gears


Ok so yesterday I was working on my car and installing a differential expansion tank. When I removed the vent for the axle tube I heard a slight pressure release.


My question - is the differential supposed to be under any positive pressure?


I cleaned the vent up and blew through it and it does flow air now. But I am wondering if the pressure issue in normal or contributing to the pinion seal looking like it is leaking.


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post #2 of 10 (permalink) Old 12-21-2015
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I REMOVE my vent every couple of months and soak it in a small can of solvent,blow it out and reinstall it.You should have NO positive pressure in the diff,that is the reason for the vent, it will also help to extend the life of your pinion seal.

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post #3 of 10 (permalink) Old 12-21-2015
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They do not run under pressure the way an engine does.
The vent is for the expansion of the differential oil as it heats up, which as it expands, air is expelled, and oil if necessary.

However, if the vent is blocked, there is a pressure build up which could contribute to causing leaking seals.

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post #4 of 10 (permalink) Old 12-24-2015
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that vent is a one-way valve for gases to escape the differential. when the differential is cold, the gas inside contracts creating a suction, when you take off the vent, you hear air rushing INTO the differential.

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post #5 of 10 (permalink) Old 12-24-2015 Thread Starter
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Quote:
Originally Posted by 740weapon View Post
that vent is a one-way valve for gases to escape the differential. when the differential is cold, the gas inside contracts creating a suction, when you take off the vent, you hear air rushing INTO the differential.

ahhhh hhha, interesting, I will have to run the expansion tank for awhile and see if it cleans things up, if not I will have to look at replacing the pinion seal - don't really want to do that


Thanks for the education

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post #6 of 10 (permalink) Old 12-24-2015
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There should NOT be any + or - pressure inside the rear diff,that is why it is called a vent and not a valve,it is there for equal pressure hot or cold.If it hisses either hot or cold it is plugged and needs to be removed and cleaned in solvent.
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post #7 of 10 (permalink) Old 12-24-2015
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Quote:
Originally Posted by 5.0 Coyote View Post
There should NOT be any + or - pressure inside the rear diff,that is why it is called a vent and not a valve,it is there for equal pressure hot or cold.If it hisses either hot or cold it is plugged and needs to be removed and cleaned in solvent.
It's a one way valve with a spring and a rubber seal. Trust me. I took mine apart when I put on the turkey baster version.

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post #8 of 10 (permalink) Old 12-26-2015
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Quote:
Originally Posted by 740weapon View Post
It's a one way valve with a spring and a rubber seal. Trust me. I took mine apart when I put on the turkey baster version.
i agree with you, i didnt know it even had a spring though. I thought after enough psi build up it would be able to push up the little metal cover and escape. When it cools down itll suck it back down. Mine had some pshhhhhh when i took mine off. I installed in on my bobs tanks and blew through it and it allowed air to go through. Its definitely not "easy" for the air to go through but it lets pressure out.

So theres really no way to get all the pressure out without having an open filter and that would get messy.

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post #9 of 10 (permalink) Old 12-29-2015
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It's a stupid design. You'd think they would have figured out a better solution with how long this rear end has been in service.

I got the dealer to put the turkey baster on mine, even though my VIN wasn't covered under the TSB. In short order the thing got melted by the exhaust and started leaking again.

I finally scrapped it all and ran some nice fuel hose from the vent, all the way over to the wheel well, secured with zip ties. That long of a run didn't even need a vent filter termination. Finally done cleaning off diff fluid and road grime from everything near the rear axle!
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I went with a Boss/GT500 finned differential cover, which has the vent hole up on top. Then bought the "turkey baster" vent and installed it in that top hole. It looks tight up under there but it has not hit as far as I know.

I probably should have plugged the old vent, but left it there for now due to laziness.

So far, no problems / no leakage after at least a dozen 20-30 minute track sessions.

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