rear diff leaking - help needed

[g0ndor]

so,

i had new tires installed this weekend, and the tech told me that my rear diff is leaking, the guy works/tunes subaru's btw.

 

i went to the delarship and after a quick look they say it is physically damaged, the exaust is dinged and have i hit anything.

so i told them i can wait for them to see what the damage is and what they need to do - i haven't hit anything.

One hour later, they tell me there is no damage, they have wiped it clean and i should go back after two weeks for check up -

supposedly there is a hole on top of it and i just spilled some fluid - not much and it is still full.

 

After i installed cusco sways a couple of months ago, i have gone over a couple of rough bumps where the car was shaking pretty

good - so if it is possible to spill fluid, it is also very likely i spilled some.

I haven't noticed anything while driving, except for a single clunk after starting the car and making a turn soon after, but

this has been going on for a while and it sounds like it is coming from the front.

I will lift the car and have a look myself next weekend, but in the meantime any advice or suggestions are welcome.

 

btw, i have reviewed similar threads, but they don't seems to apply to my case.

 

tia.

G

[atc5]

so you drive your car with a hole in the top of your rear diff?

[rice_rocket]

Yeah that sounds a little fishy to me. I don't know subaru's, but any diff should NOT have a hole in it. Sand or dirt or even water getting in would f'up your diff. So if it comes out of a hole, things can come in. I don't like what the dealer is telling you about it...

[fishbone]

Once you screw the drain and refill bolts on the differential, there are no other places where the fluid can get out, it should be a sealed unit.

[g0ndor]

thanks guys,

i have also been checking the service manual, it seems that besides the drain and filler plugs there is also a breater hole on top, with a cap.

i'd seriously doubt it could spill fluid through the breather hole, so loose filler plug is the only explanation so far which makes sense.

I will be inspecting it myself regularly from now on, but i also want to be ready to ask the right questions when i go for the check up.

[fishbone]

Breather hole? Interesting.

[Fivspeed]

Glad you found the answer. Its common for diffs to have a vent. The fluid in your diff, much like your engine & trans oil, expands as it heats up and causes pressure. Pressure, if left unvented could/would cause seal leaks and possibly blow out a seal.

[g0ndor]

Glad you found the answer. Its common for diffs to have a vent. The fluid in your diff, much like your engine & trans oil, expands as it heats up and causes pressure. Pressure, if left unvented could/would cause seal leaks and possibly blow out a seal.

 

it makes sense about expansion with temperature, but i have to phycally see the cap which covers the 'air breather hole'

in order to know if that cap also allows for ventilation. the service manual instructs the cap to be removed during draining -

no idea why you wouldn't just remove the filler plug to achieve the same result.

 

in any case, this is all speculation on my part - i hope someone with experience will chime in..

thanks.

[fishbone]

So it's more like a valve or a diaphragm, not really an open gaping hole.