Differential breather, stuck after track day?
 

So had an excellent experience at Sebring in the BRZ, laid down some really nice times considering it was my first time out ever. But it was cut a bit short.

At the end of day two, we started to smell oil in the cabin. Shortly after i got black flagged and went in for inspection as corner workers could smell it too.

No leaks anywhere, but a strong gear oil smell from the diff and upon closer inspection, the differential breather valve. Drove it a couple times and continue to get strong odor when warming it up, so today im draining and refilling, and sending off to blackstone what was brand new motul 300 75w90 less that 600 mi ago.

Do these breathers get stuck open or something? Should i be looking to replace the breather itself? Did i likely boil this fluid on the track? Anything else to look for? Not much come up when searching this topic so any advice is greatly appreciated.

Was it diff fluid or maybe CV grease?

You're going to want to run 75w140, these cars tend to cook diff fluid.

Wrap the exhaust in that area too.

:w00t:

Great advice,will try the 75 140, and wrap.

Smell is definitely coming from the Diff area, no smell from axles and boots in good shape.

Edit: drained the diff, only about 750mi on the fluid and its the color of maple syrup, so yeah, i think i found the problem! Wrapped the exhaust too, never thought about the proximity of the exhaust to where the drivers side axle goes into the diff.

Not alot on the magnet, so hope all is ok.

The Gen 2s seem to have an issue more than Gen 1s. I've been okay where as a friend with a Gen 2 BRZ had issues the first track day.

Diff oil is stinky, said friend passed me when I was on a cooldown lap and you could easily smell it in my cabin. Same thing, it was coming out of the breather tube - doesn't take much to cause the smell to occur.

Doc's suggestion is the best

This just happened to me this past weekend while at the track (2022 GR86). Seemed to start after I went 4 off backwards into the dirt, so I thought I cracked the diff cover or something the smell was so strong (but no leaks to be found anywhere).

Odd thing is that I already have hundreds of laps and autox runs on the car. I wonder if it was due to running high grip tires for the first time and giving the diff a real workout? Previous tracking was all on the OEM PS4 or GT Radial SX2...anyways, time for a diff fluid change and see if the smell goes away.

I think you are probably right on about working the diff harder. Is the exhaust anywhere near the diff like it is on the gen 1.

That gear oil is going to stink coming out. Prepare accordingly

The exhaust pipe is a 4-5" away from the side of the diff housing (Borla). I may wrap it as well, per @DocWalt suggestion. I had over 12k miles plus all the track/autox on that original fluid, so guess I shouldn't be surprised if finally cooked over. Just took me a bit to remember what that smell was...

Yea it was stinky, trying to air out the cabin over night :(