97 OB, Front diff spitting oil from top?

[Commuter]

Ok, so here is my situation.

 

97 Outback, auto, 580,000 km.

 

Last summer, after putting a used engine in, I noticed some oily mess from the front diff. I don't think the engine change had anything to do with it; just coincidental timing. There is a bit of oil coming out near the top, towards the passenger side. This is just back of the dipstick for the diff. There is a little block and a couple of tubes at this point. I believe it is a vent for the diff??

 

At the time this first started, I had a slow leak in one front tire. I wondered if the 'spitting' was due to the diff working some from uneven tire pressures causing different effective tire circumferences. (I believe this is what happened to me several years ago on the rear diff. I picked up 2 nails in the same tire in a 3 week span and the tire pressure got down to 20 psi and even less at one point. Same behaviour... the dealer said the seals were bad, but to this day I'm not sure that I believe that was the case.)

 

So anyway, the tire was resealed a while ago. The bit of oil mess seems to be continuing. I wiped it off recently and there is now some fresh oil there. I topped up the front diff as well. I'd only lost 0.1 liter over 40,000 km.

 

I don't know if there is any connection to the synthetic oil that I use. That is, whether it is more likely to foam from a diff that is having to work some from uneven tires. I might change it out, but not until the weather gets better. I should also mention that I do a lot of highway driving. About 50,000 km a year, most of it highway.

 

Any clues? I certainly hope this isn't a sign of anything going wrong. The car drives the same as always. I just have this bit of oil mess plus a burnt oil smell since some gets onto the exhaust.

 

Thanks.

 

Commuter

[njdrsubaru]

it may be your inner cv boot that is ripped

[porcupine73]

Hi. So I hear from my coworker in Mississauga you guys got like 8" snow up there! Yes one of those is the front diff vent and the other is the auto trans vent. One thing that can cause venting is overiflling of the front diff. However, I am curious if the synthetic front diff oil you are using is Lucas by any chance?

 

[OB99W]

I'd suggest checking both the diff and trans fluid levels. If there's a bad seal, there may be some ATF getting into the diff. That could raise the level in it and make aeration more likely.

[porcupine73]

Good point, there have been posts in the past where this happened, the ATF getting into the front diff gear oil, some input shaft seal or something....