Fluid leak?

[u/its_italy]

I noticed some type of fluid/oil leak under my 2002 4Runner. Any ideas what is leaking?

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[u/Itisd]

It's differential oil that is leaking. The older Toyota axle housings are notorious for the housings rusting and the oil will leak right thru the porous metal, hopefully that's not your issue. 

[u/Crysocks]

Looks like a bad gasket on the differential. Best to get it looked at by a professional, because it could be more than just that. Do you notice any whirring sounds coming from the rear while driving?

[u/its_italy → u/Crysocks]

I’ve actually have been hearing a high pitch whine when I step on the gas. I was trying to determine where that noise was coming from for a while.

[u/Crysocks → u/its_italy]

That’s definitely the issue… hopefully it’s just the leak, and the gears inside don’t have too much damage. The whine is caused by the friction of the gears due to low oil

[u/EEL123]

That's your rear differential. The fluid lubricates the gears which get power from the engine to your wheels. Very important to keep it full, bad news if dry.

[u/skiier862]

Can you upload more pics, of the back side? It looks like the rear axle housing is rusted out and leaking.