[kirtydandra]

Hi all. I recently got back from a 1000 mile road trip and started to notice a new burning smell. Upon closer inspection I noticed that my front diff is puking from around the dipstick tube area.

Diff is not over full and not even a tint of red so I don't think the trans is filling it.

Has anyone else experienced this? Is there a dipstick tube o ring like a trans has? The o ring on the dipstick itself seems to push in tight.

Need to get this fixed ASAP. thanks.

 

[kirtydandra]

Looking closer at the dipstick o ring it seems
Quite hard and flat. I'm gonna head to the dealer this weekend in hopes to get an OE o ring.

I'm also gonna check the vents and tubes and make sure they look free of debris.

I hope this fixes it and I don't have to pull the trans. I'll post my results.

 

[RobLog]

Looking closer at the dipstick o ring it seems
Quite hard and flat.

My o-ring is the same and the dipstick is pretty loose fitting, but the diff has never puked oil. Puking is a sign of too much oil, but you wrote it wasn't overfilled, so ??? Are you sure it's gear oil that's leaking? Maybe the leak is something else nearby.

 

[subiesailor]

Gear oil will smell pretty putrid and is very different smelling than AT fluid or engine oil.

Guessing AT? Could be a vent that is plugged also the diffs do have vents on them.

 

[1 Lucky Texan]

check all your fluid levels closely, including the power steering fluid and engine oil.

check the CV boots for splits.

 

[JavaTee]

Also check around where the axles mount to the transaxle, it might be the axle seals.

Later, T.J.

 

[kirtydandra]

It is definitely gear oil that I'm smelling burn. Yes very putrid. I'm used to the burnt engine oil smell and the ATF smell as my rack has recently developed a leak. The source of this leak is from the top of the bell housing by the vents but not coming out of the vents. Do these vents get plugged? If so what's the fix? Blow it out with some air?

As I stated before definitely not over full. The level was at the min line after puking some out. So it looks like its leaking more than it is.

I suspected the right axle seal but put that to rest seeing as the top of the bell housing is wet.

 

[plain OM]

The source of this leak is from the top of the bell housing by the vents but not coming out of the vents.

There's two vents -- one is for the transmission itself, the other I believe, is for the differential. (See attached photo.)

If a hose is blocked, pressure could build up in the affected enclosure, but that would force oil out other paths, for example, the axles or the dipstick on the differential.

The vent hoses are fairly long -- any chance the differential vent hose has come off the nipple so the oil isn't coming out the end of the hose, but at it's source? (In the photo, the source for each is to the right, whereas the pipes end toward the left.)

Other than the vent, i'm not aware of any other place at the top of the bell housing for gear oil to come out, other than . . .

. . . a cracked case, but even then it would still require the oil level to reach a crack at the top to come out there.

 

[subiesailor]

Just a side note. All of the MT cars I've had over the years would start to leak in various odd places when the gear oil was DONE. After changing the gear oil they would stop leaking.

Any idea how old the gear oil is in the front diff? It might be way beyond its life and so thin that this could also be a cause.

 

[kirtydandra]

Naw I've had the car for 1.5 years and serviced EVERYTHING upon getting it. I am a mechanic and get to service it for free so my fluids stay fresh

I did get some shop time with it today and pulled the diff vent hose and blew air in it. It was totally clear. Then I blew air gently in the nipple on the trans with the dipstick out and felt air there. So I am certain all that is in working order.

I am definitely convinced it all pushed past the dipstick. I cleaned all the gear lube off the case and put the fluid at the full mark.

A thought Im having on this. About 700 miles of my
Trip was in mid 90's hot dry type weather. Is it possible it expanded that
Much seeing as I fill it to the full mark? I assume that the marks would account for this?

I am quite perplexed but drove 30 miles today and still dry as can be.
I'm starting to think its just one of those quirky soob things?

Still am gonna get that o ring though 220k going strong I think it's worth it

 

[plain OM]

I cleaned all the gear lube off the case and put the fluid at the full mark . . . I am quite perplexed but drove 30 miles today and still dry as can be.

Probably the best idea -- watching it more closely now will be more likely to reveal exactly where it's coming from; that is, if there is any more leakage.

Is it possible it expanded that Much seeing as I fill it to the full mark?

I doubt it would expand that much. Lots of Subarus are running under similar conditions.

If there's no contamination from other fluid (Did you do a full drain and refill this time to confirm?) and you're sure it came out the dipstick tube, then I would conclude that it might have been inadvertently overfilled, as was suggested by RobLog earlier. Even as careful as I try to be, I found it's all too easy, with the low down the side location of the tube, to end up with somewhat more than I intended, and having to draw out a bit to get exactly to the "F" line. Also I found that the dipstick reading will change noticeably if the car is on even the slightest slope. It wouldn't require much given that the differential takes only a quart.

While I haven't confirmed this, I believe there's two reasons the oil level in most differentials is usually set to not more than about half-way. One is to avoid the side axle oil seals being immersed continuously; they're snug, but not intended to prevent any leakage at all, and if they were immersed, there could be leakage to the exterior even when the car is parked.

The other reason is to allow room for the possibility of foaming. This can happen especially with older or poorer quality gear oil when it's very hot, and when the car is driven at high speed for long periods in very high outside temperatures. The foam, of coarse, will take up far more space. If there isn't enough room within the differential, the oil will find its way out the next highest opening, which is the dipstick tube. If the differential had been overfilled to begin with, a smaller degree of foaming could lead to an apparent leak from the dipstick tube.

Incidentally, I don't believe the dipstick o-ring is supposed to be an oil-tight seal in the tube. Rather, I think it's there to provide only a bit of a grip, to prevent the dipstick from rattling around in the tube and moving up out of the tube. There have been reports of the transmission dipstick being very difficult to remove because of o-ring binding. I think a bit of slack is preferable to a squeezed-tight seal.

Good that you cleaned it up and reset the level. Keep an eye on it, and let us know how it turns out.

 

[kirtydandra]

Ooh foaming theory is a very very good thought. I most certainly was at a constant 75mph in that heat. But again the fluid is definitely no older than 2 years and has less than 30k on it. How often is everyone changing their diffs?

I did not drain it but I made an educated assumption by the fact that the fluid was lower than I filled so contamination is unlikely. Also I used a fluid evacuator to set the level and that was all perfectly clear, gear oil type color.

Thanks for all your opinions. Big help at putting me at ease on all this. I was quite worried.
I'll post back in a couple days hopefully with the same dry results!

Cheers

 

[plain OM]

Look forward to the update.

But again the fluid is definitely no older than 2 years and has less than 30k on it.

2 years should be fine for a good quality gear oil meeting Subaru's specs. (Typically, 75W-90, GL-5). However, foaming can happen at high temperature even with new gear oils . The rear differential is probably less prone to this because of the road surface air rushing over it, whereas the front differential is sandwiched between the engine and transmission, has little exposure to the outside, and what is exposed is probably subject to hot air flowing back from the engine area. Given the right combination of heat and churning, and foam can result.

How often is everyone changing their diffs?

I go overboard on this and change the front and rear differential oil every year, which is about 12 - 14,000 miles. It's only about a quart in each, fairly easy to do (better than my 76 Suburban that requires removing the rear differential cover!), and up to recently, not all that cost prohibitive. However, I've been using Castrol Syntec, and here in Canada, a litre (close to a quart) has gone from about $10 a few years ago to close to $20 -- I have to start re-thinking my approach.

I also do a simple drain and refill (about 4 qts) of the ATF each year.

 

[kirtydandra]

Ya I definitely over service my car as well. ALL of my fluids look and smell as if brand new. I know my car inside and out which is why this troubled me so. Ha.

Another 60 miles today and still dry as can be.

Im sticking with the foaming idea. Only thing that makes sense.

Seeing as I offroad quite often with it I definitely am gonna get a new dipstick o ring just to further seal it up for when I'm pushing it's limits. In my opinion it'll be a reliability upgrade.

I believe this has been resolved as a somewhat normal happening under extreme circumstances. It just so happens I keep a quart of each type of fluid for such occasions. Not that I used it this time. Having a full size spare and removing the donut really opens up the cargo room! I carry all sorts of emergency gear. Quite comforting

 

[kirtydandra]

just wanted to cap this thread off with some final thoughts/results.

been a week and half and still dry as can be. i did put a new oring on. but that was only yesterday so wasnt the fix per say.

i do have a primitive engine skid plate and theorized that may be directing more heat than normal to my front diff? at any rate i am convinced it was due to overfoaming under apparently the right conditions (i had noticed it damp once before after i came down from the mountains after some good trail running but so minor i didnt think much of it)

i do believe this is just a temporary concern under stress and shouldnt see it again now that my dipstick seals in tight.

thanks for everyones input (as always)!

Cheers,
Dan