Subaru Outback - Subaru Outback Forums

Subaru Outback - Subaru Outback Forums (
-   Problems & Maintenance (
-   -   Front differential leak (

ratmjmt 07-17-2007 05:15 PM

Front differential leak
I have a 2000 Outback limited (AWD) with close to 130,000 miles.

Has anyone else had this problem?

Oil from the front differential seems to leak when the car is driven in hot conditions or after driving for a long time or at highway speeds. And I’m not sure where it comes from and/or why.

At first I thought it was my differential dipstick because the O-ring was shot and the dipstick would just dance around in its place/housing. I noticed oil all around the dipstick stem/housing. I replaced the dipstick with a new one from the dealership and noticed a tight, snug fit when I installed it. Everything was great for a week (even at highway speeds), but on a recent hot day after getting off the highway, the oil leak returned, and this time it seemed to come from above the transfer case/differential housing. The dipstick remains snug and tight and dry. I wonder if after replacing the dipstick, the oil’s only way out was now from above.

I cleaned up the oil and haven’t had that issue the last couple of days, but our weather has been cool, so the car or its parts are not getting unusually hot.

My mechanic thinks it’s leaking through the differential’s vent (Is there such a thing?) and probably after the transmission gets a little too hot. I recently had the transmission rebuilt, but I had this problem before, just not as severe. He checked the differential oil level to see if it was too much, but the oil level is fine.

Any ideas to fix this?

lomita 07-17-2007 06:16 PM

Ventilation Problem
Sounds like now that the dipstick has been replaced, the oil is looking for the next best place to come out, meaning, the pressure is building up possibly. I don't know how the tranny is normally ventilated, but it appears it is clogged. What kind of oil are you running in your tranny. You don't suppose it is foaming do you?

ratmjmt 07-17-2007 06:39 PM


I’m not sure what kind of tranny oil was used when they rebuilt my tranny. I, too, have wondered if a use of cheap or wrong/incorrect tranny oil would lead the transmission to heat up bit more than normal and cause the differential oil to boil/expand.

My mechanic thinks the tranny might be causing this.

Do you know if the transfer case has a vent?

porcupine73 07-17-2007 07:23 PM

Is this a manual or auto trans? Either way are you sure the gear oil isn't overfilled? Yes there is a vent on the top of the trans. For the AT's there is a vent for the AT and a separate vent for the diff. These normally go into two hoses pointed slightly downwards.

The '00 (if it's an auto trans) would have the Phase II 4EAT. I have a pic showing roughly what these hoses look like (it's from the phase I but same general idea). If there is interest I can post the pic; my acrobat keeps crashing right now so I can't at the moment.

lomita 07-17-2007 10:46 PM

Oil Leak
I take it by your description of the dipstick you have a manual transmission. Verify that for the rest of us.

Who did the rebuild on your tranny? Did they take the tranny in and out of the car? What is their guarantee? Ask them exactly what fluid they used, brand name, quiz them on how much is standard refill amount after rebuild.

If I didn't personally put the fluid in, I wouldn't have a clue as to what fluid is in there. That is the first thing I would go after, drain the present oil, flush it with some new fluid, the kind that you know is proper, then watch for the condition again.

I would totally get the housing cleaned off either with some solvent or with a steam cleaner. Sometimes frowned upon, but the self service car wash with super hot water under pressure can do a pretty good job. Then if any more oil comes out, you can immediately detect where it is coming from.

I could not find any vent hoses or points in my Subaru manual for my Impreza Outback, but that doesn't mean anything. Just have to get down there with a mirror and flashlight and go over the entire case looking at everything till you are satistied there is or isn't a vent. I think there has to be a breather there somewhere. But at least if I look, I may make discoveries in the process.

porcupine73 07-18-2007 08:37 AM

Here's the pic I was thinking of. It's from an pdf. This is a 4EAT phase I. Those two s-shape snake like hoses at the topish leftish of the pic are the vent hoses. One is for the AT and the other is for the front diff.

The main purpose is to keep the internal case pressure the same as atmospheric so the seals don't get pushed out. But other issues can cause fluid to come out those vents too.

ratmjmt 07-18-2007 11:27 AM

I do have an automatic transmission. And after seeing the pic, it seems like my transmission might be the cause of this. Again, the mechanic said that the transmission’s temperature might be the reason why the diff. oil is leaking. It’s definitely not tranny oil because the oil that’s leaking is clear; my tranny oil is red.

I believe they used Dexron III oil (I hope I spelled it correctly) in the transmission.

One thing I failed to mention: I’ve developed a tranny oil leak at the pan (after my rebuild tranny warranty expired), and I’m in the process of fixing it. I wonder if a loss of tranny oil would increase the operating temperature of the tranny and cause the diff. oil to heat up and exit through the vent?

porcupine73 07-18-2007 11:40 AM

Are you sure it isn't engine oil that is leaking then? When the trans was replaced/rebuilt, the engine rear main seal should have been replaced. And if the engine had a plastic rear main seal retainer/oil separator, it should have been replaced with the upgraded metal version.

If the AT is low on fluid, you would notice slip before overheating (overheating because of low fluid that is; if there are other issues, such as the torque converter wasn't seated properly and cracked the pump, or the ATF cooler in the rad or lines are plugged, that would be different). Also there is an AT high temp indicator on the instrumental panel.

Another question...did you have the trans you had in there rebuilt, or did you have a different already rebuilt one installed?

ratmjmt 07-18-2007 12:01 PM

I’m pretty sure it’s not engine oil because of the smell. The diff. oil in my car has a distinct (nasty, really) smell, and the oil it leaks smells the same.

Also, when I first thought it was leaking through the old diff. dipstick, I wrapped the dipstick with a cloth, which was coated with the oil after a week, and had that distinct smell.

Tranny is definitely not slipping. The trans that was in there was rebuilt.

I will again check my diff. oil level tonight.

Do you know if on a the rebuild (they also replaced the torque converter) they would have had to replace/drain the diff. oil? Maybe they used the wrong diff. oil.

All times are GMT -4. The time now is 01:43 PM.

Powered by vBulletin®
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.

vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 2009-2010 All Rights Reserved.

For the best viewing experience please update your browser to Google Chrome