Rear diff oil leak seems to originate from the magnet at the top

[Yogibeer]

Have had my Pathfinder Chinook 2004 for 8 years and love it. Live in Edmonton, Alberta and she has dealt with wild weather laughing. Noticed the rear diff had some oil, so today went under to inspect. I thought maybe the brake lines were leaking but the oil seems to be coming from the top of the diff, where there is a silver cap that comes up when I pull it up but then snaps down when I leave it. Is that an overflow valve or the magnet that is supposed to hold debris ? Will visit a dealer to check on the recall, as we do get nasty subzero temperatures and salt is used. Thanks

[4xq]

Check on the Takata airbag recall as well. That has been expanded, and I think you will get new airbags.

There is normally a vent hose on the top of the differential that runs up into the frame crossmember in front of the spare tire.

That spring loaded cap sounds like an aftermarket thing to me. In any event, you should not be leaking fluid from the top of the differential, so I would have someone do a drain and refill just to be sure everything is ok fluid wise and that the diffy is venting properly.

Probably time for that from a regular maintenance standpoint anyway!

[Yogibeer]

Thanks. Yes that makes sense. Maybe the diff oil has lost its viscosity as it has been 5 years and a hundred thousand Km plus since I got it drained and refilled. Am pretty sure it's draining from the cap, but I did clean all the oil and goo off in order to find the trail once at the shop. Thanks a lot

[Hawairish]

That thing on the top of the diff is a breather, and it's OE. What 4xq described is also a breather (also OE), but really just a barb with a hose running up high. Both allow air to escape the diff, though the hose style is obviously better at keeping water out.

The short breather is found on numerous Nissan trucks/SUVs. Mine had it, but I replaced to the barbed style (my 98 Frontier has the short one). Neither have a magnet; only the bottom drain plug has a magnet.

Oil come from there is normal. Just oil sloshing around over time. Nothing to worry about, but consider a fluid change if it's been that long.

[Yogibeer]

Thanks Hawairish. So it is a breather. Hopefully the new oil would be viscous enough to stay inside. Any suggestion on flushing the diff once the old oil is drained ? Is that practical? Or should I just get it drained and refilled ? Thanks

[Hawairish]

Yup, just a breather. The cap keeps dirt and water out...but not too useful when submerged.

Not so much an issue with viscosity, just the seeping/vapor nature of oil. Inside the diff, there's actually a baffle/shield welded below the opening to keep oil from splashing directly out of the breather. I've got an axle in my garage if you want a pic.

Simple drain and refill is sufficient. Just open the fill plug before the drain plug, and clean off the magnet on the drain plug (check for metal flakes). A black slurry on it is generally normal, there just shouldn't be a ton of it or really anything shiny in it.

If you've got the LSD, generally cheaper to get an oil with an additive already in, versus oil and separate additive. It'll be labelled "LSD safe" or similar. You can use the same oil in an open diff, if you have a preference for an oil. Most premium oils (RedLine, AMSoil, Royal Purple) are already LSD-safe. I've recently used an 80W-90 Valvoline (VV831) that is inexpensive ($6/qt) and seems to be holding up well (recent Lokka and LSD installs).

[Yogibeer]

Thanks all. An update. The breather cap was blocked and as we opened the fill plug bolt, we heard a hiss. So pressure was building up inside the diff and probably when it reached a significant level it was coming out of the breather cap bringing some oil with it. Caught in time. Thanks