I have a 2015 SR5 Premium (~60,000 miles) and I am afraid my rear pinion seal is leaking. I crawled under the car for the first time in a while and noticed the forward side of the rear differential was wet with oil similar to the photo I found in the 3rd gen section and attached below. My leak isn't as bad as the 3rd gen one shown below, but it is in the exact same location. I'm yet to see a single drop on my garage floor where it is parked daily.

I also started noticing a faint metal-on-metal sounding, cyclical, high-pitched squeal at low speeds that didn't change with any degree of brake pressure. It is pretty intermittent and sometimes I hear it, other times not at all. Could this sound be related to the pinion bearing or seal?

Has anyone seen or heard of anything similar in a 5th gen? I cleaned the area of the leak with WD-40 and will monitor it over the next couple weeks to see if it comes back. I checked the diff breather and it had some mud on it but didn't seem to be bound.

My truck is nearly stock with only appearance upgrades and TRD Wheels with K02s (stock size) and only has 60,000 miles. I've only taken it off road/"wheeling" a few times and didn't feel like I pushed the limits of the vehicle by any means and it has almost a year since the last real off road trail.

I want to thank everyone in advance. This is my first post and I've been visiting the forum almost daily since purchasing the car.

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It can happen if your rear diff breather gets clogged. Look at see if its rusty and not "breathing".

Sure looks like a pinion seal leak. They can be replaced without removing the diff so long as the bearing isn't damaged. I'd keep an eye on the fluid level and see how much more leaking you'll get. It's not a real expensive fix if you just need the seal replaced. If the mechanic says you need to replace the crush sleeve and pull the diff out - find someone else.

Good luck.

I had mine replaced last year. It was replaced with the differential on the truck at Toyota.

I also had the metal on metal squeal shortly afterward, it was the bearing dust shield contacting the housing. I used a plastic trim tool to bend it slightly and got some white lithium in there. It hasn’t done it since.

The squeal was very alarming though. Just as you described.

Thanks for the immediate feedback guys. Your insight is appreciated.

If I am mindful of the diff fluid level, should I be OK to continue driving until I can get it looked at in a few weeks?

I have new diff and t-case fluid ready to go with plan to drain and fill myself but maybe I'll hold off on the diff fluid in case the diff needs to be opened to investigate.

Talked to a mechanic and showed him the photo I attached of the 3rd gen leak (that looks just like my 5th gen leak) and he gave me a preliminary diagnostic.
He agrees it is likely a bad/damaged pinion seal and that he will just have to remove the driveshaft in the rear diff, as well as the yoke and seal. Then obviously replace the seal.

Thank you for the advice. I will be sure to follow up once it is resolved/reparied. Cheers.

Posting my experience in case others run into the same *non* issue. This post is a good display of my inexperience/stupidity and how much I tend to overthink things.

Rather than take my car to the mechanic to have the pinion seal replaced, I cleaned off the oil on the outside of the diff housing. I waited a couple weeks and it stayed completely clean and dry. Then, I drained and refilled the rear diff and it was only slightly low, if at all, before draining. After a couple more weeks of driving including some 4x4, still no sign of a diff oil leak. I no longer think I have an issue with the pinion seal!

Then I replaced all brake pads (without replacing or turning the rotors) and the rear pads were at the wear bar on both sides. That explains the cyclical sounding squeal. The car now runs and sounds like new.

In summary, none of the things I've listed in this thread were actually an issue. I needed to monitor the suspected pinion seal/diff leak before crying SOS and should've investigated the brakes when I heard the squeal.

Good for you on following up. Thanks.