Front Diff Breather oil leak

Hey everyone,

Ive been dealing with my front diff breather leaking oil since I got my 5.29 gears done (80-140 oil). Only seems to do it when I travel on the highway for extended periods of time (gear oil gets to actually heat up).

Yesterday I finally got to do some diagnosing. I checked the breather and the cap seems to move just fine, wasn't seized up. I then pulled my fill plug on the front diff and as I broke it loose I noticed some air escaped. Wondering what would cause that and if that would be making the breather puke some oil? Thanks for any and all help.

 

I assume you pulled the diff plug after everything was cooled down so likely you heard air entering and not escaping. Yes, this is indicative of your problem and showing the diff pulls a vacuum when it cools, so air can leave the diff via your breather but not enter it. Over time gear oil gets slung into your breather tube and pushed up as the diff heats up and needs to vent. The oil in the tube doesn't drain well because air cannot enter back through the breather. So oil comes out on these longer trips that generate heat as the diff vents out the breather. You can try running less fluid or install a vent line cap that will vent both directions. Often this is all the problem is.

 

Got it, thanks for the quick reply. Would a vent cap that vents both ways be something like the in line fuel filters ive seen some members post on here for diff breathers?

Also forgot to mention I have an arb air locker in the front too, not sure if that would cause more issues with oil not being able to drain back down the vent tube as easily.

 

Are you sure the diff isn't over filled?

My Breather was stuck shut and caused my front diff to push oil out past the axle seal. I run 80-140 oil as well after I did my ECGS bushing. Once I replaced the breather its stopped leaking. It did seep out of the seal a little after but I'm pretty sure it did that because I over filled the diff just a bit.

 

I know some people get rid of the crappy metal/ plastic breather and replace it with a small air filter.

 

At first I thought I had over filled it since the locker was installed it uses a little less oil. I think ill try replacing the breather with a filter of some sort first and see if that fixes it like it did for you.

 

Yes.

I have same locker and same oil in mine with no issues.

 

While my truck is a 2nd Gen, I too had this problem when I switched to 85w-140.
It did it every time I filled it back up to the point where it just starts coming out the fill hole.

Upon the advise of a trusted person, who also had this issue, I was advised to either let it leak until it “settles down” and finds its happy point. Or switch back to

$30 75w-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75w-90.

I let mine leak until it didn’t anymore. Then checked the level.
I can still feel/touch the fluid from the fill port. So I don’t think it’s too low.
Might be 3/4” below the fill hole?

Oddly, mine only leaked when it was cold outside and then warmed up when driving.
It never leaked at all when it was Hot outside (summer).