Hi guys,

I was under my truck the other day and I noticed my rear diff has been leaking slowly. I noticed it looks to be leaking at the breather. I recently had a East Coast Gear diff installed so I do not believe its the pinion seal.Fluid running down from the breather to the bottom and then throwing it back.

Is it possible that the breather seal is leaking? Warmer weather causing the fluid to be pushed up out of the breather? Is the breather an NPT thread that maybe needs some Teflon?

Also recently getting P0440 and P0446 after changing plugs. Gotta do some more research on where to start with these. Could be a evap hose pluged or disconnected? Gas gap?

Thanks in advance.

Alex W.

Fluid should not come out the breather.
Did you check the fluid level?

I did check the fluid level because I was concerned it was low. I removed the fill plug, no fluid came out. I continued to add fluid until a little fluid dripped out out, replaced fill plug.

Breather sticks out the top of the axle housing, so am I wrong to think that in order to over fill it enough for it to come out of the breather it would be difficult considering the fill plug is much lower.

Im pretty certain it is the breather, lunch time coming up I will snap a picture and upload so you guys can confirm it.

I believe the correct fill is just below the fill hole about 1/4"

If it was the pinion seal, you'd see oil slung all over the place since it's a rotating part. That should rule that out pretty quick. I would get the breather replaced asap because all that pressure not escaping could cause your axle seals to leak, and then you'll have bigger fish to fry.

Agreed on ruling out the pinion seal.

Breather is cheap enough I will get that this weekend.

If the fluid is high then I can see it being pushed elsewhere instead of out of the breather and there is zero fluid at my wheels or anywhere else for that matter.

The correct level is right at the bottom of the threads of the fill plug but the FSM says if it's within 5mm of the bottom of the fill plug threads then it's OK. Nobody is going to try to fill exactly to 5mm or 1/4" from the lip. When you fill a differential, transfer case or manual transmission, you fill until you see gear oil spilling out and then you're good. This is auto mechanics 101.

If you're getting gear oil out the breather it's because you either overfilled because you filled the diff while it was at a slant downward towards the front of the rig or the breather is sticking and the pressure is building higher than normal and when the pressure finally overcomes the sticking breather oil is joining the air escaping.

So i went and tried to grab a picture of the leakage at lunch time. The picture is tough but you can see the fluid has been running from the breather down the left of the pumpkin for some time.

I removed the breather and cleaned it out. It is moving freely without hesitation, I even blew some air and feel it coming out. still not ruling out the fact that the internals could have an issue.

I decieded to add some teflon tape to the threads to help prevent any leaks. If the diff is overfilled it will continue to leak until its at a happy level. I will monitor it.

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Some lighter weight / synthetics will do this as well.

Saul, you could be on to this. I did put in a synthetic fluid when topping it off the other day, going to pick up some reg GL5 this weekend.

the gear oil used is not the problem the breather threads are the problem . you can't over fill ....... you fill to the bottom of fill plug.

if it still leaks at around the breather then you buy new breather. could be they cracked it.

Does anyone have the part# for the OEM plug? or is doing the diff extender really the only option.

I plan on taking the truck some 800 miles this weekend and would like have this solved. My plan is to get a new plug or extender and add some fluid. The leak should stop then. I agree the threads could be the culprit.

I just replaced mine as well. 90930-03031

Thank you very much !