It's a very widely known fact that if you plan on taking your JK through deep water or mud, that you should extend your diff breathers to a place where they will not be prone to sucking in said water or mud. I just watched a video explaining why we have diff breathers, and from what I can understand, they're there so that when the diff warms up, the hot gases in the diff can escape. My question is: what gases are they? Is it just air, or is it some other type of gas? Could there be fumes from the oil in the diff that are escaping as the oil gets warm and some of it converts to a gas, or is that even possible?

The reason I ask this is because, like a lot of people have done, I'm planning on extending my diff breathers and transmission/transfer case breathers to the air box. My thinking is that if these gases are NOT air, they would be sucked into the engine through the air box, potentially robbing the jeep of power and decreasing valuable gas mileage. Am I over thinking this? If it's just air, it obviously wont do any harm, I just don't want to potentially hurt my jeep…I'd rather move them somewhere else if this is an issue.

 

Do this...not an issue

 

Interesting question. I'm also curious about the vacuum effect the box puts on the breathers.

 

There's not much "vacuum" applied to those lines. The "gases" are more just fumes than anything and it is no more harmful than your PCV valve venting into the air box. You won't see any mileage differences.

Good questions though, thank you for the contribution to the forum.

 

Thanks for the quick responses, this was what I was looking for

 

Not sure what video you saw, but there's an even better reason for venting the differentials. If you've ever felt them after driving you probably know they get very hot. If you enter cold water, they get very cold. Take hot air/gas mixture and make it cold and there is a vacuum. Don't give it a place to get air/gas from and it will bring in whatever it can. If the diffy's are airtight, that would then be through your axle seals. Which could mean pulling water into the diffy. It used to be years ago that before fording it was recommended in some quarters to stop at the water's edge and let the diffy's cool off for a while to prevent this.

 

I got this kit, but this pic is missing one. It also comes with one for the trans breather too

Sent from my obama monitoring device

 

Tranny breathers on autos are easy to include--there is an existing line to reroute. Us manual drivers need to find the nipple on top of the tranny. Think I'll do mine when I next pull the tranny to fix a leaky rear main seal (forgot to do it when I swapped the clutch).

 

OK, I really don't understand why you would take them to the air box. If they are extended up high they should be OK. Of course Devil you might be different since you spend a lot of time in the Barrens in water.

 

Extending them up high is good but it's still possible to sink most everywhere else on your jeep but be cognizant of your air box. It's just 'extra' insurance that you won't get water in the lines because if you get water in the air box then you'll likely have much larger problems than milky diffs.

Edit....my front diff breather now sits level with the top of the hood and the rear is essentially at the top of the tub in the passenger taillight cavity. If I get that deep then my entire dash will be under water as will the intake, alternator, TIPM, and the other two computers under the hood. At that point I'll be more concerned with everything but my axles.