O-Ring Fell Out During Diff Oil Change

Just like the title says. This o-ring fell out of the drain hole when I was changing the rear diff fluid. It's on a 2017 TDR-OR with the locking diff. I poked around for a bit but I can't make heads or tails on what it's for. There's a part of me that wants to say that it was already broken when I drained the fluid, and it wasn't leaking so let sleeping dogs lie.

Anyone else had this happen?

 

That seems kinda weird. I've drained a lot of diffs over the years but never had something like that exit!

 

Which differerential? I know one of the differential access plugs is big but it ain't that big. Honestly, that looks like a buggard up old filter cartridge o-ring left over from an oil change to me?

 

I have no experience with the internals of the Toyota E-locker internals, but that does not look like anything that would come from a regular open differential. There is a thread on here somewhere that shows all the locker internal parts - someone took one apart and documented it.

Pinon seal? No, would have to get past the bearing to enter the pumpkin.
Axel seal? Is the only possibility I can see.

Can't make out the profile of the seal, looks to be "L" shaped.

Is it possible this O-ring was left in the bottom of your drain pan from some other prior work?

 

[QUOTE="Toycoma2021, post: 30209654, member: 351607"
Is it possible this O-ring was left in the bottom of your drain pan from some other prior work?[/QUOTE]

This has my vote unless, of course, the OP actually saw it exiting the drain port.

 

I personally saw the broken oring hanging out of the rear diff drain plug after the oil finished draining. I pulled it and this big ring came out.

 

If the the diff locks fine and doesn’t make noise, I say send it. Looks like a wheel bearing O ring, watch for an axle seal leak.

 

Rear axle o-ring?

 

Toyota Tacoma (2015-2018) Service Manual: Components - Rear Axle Shaft - Axle

 

How would that get past the more inboard oil seal?

 

And all the way down the axle shaft?

 

Maybe the axle oil seal rubber split apart?

 

If this is the case a careful inspection of the rubber edges may show a jagged edge on one side. OP could get out a magnifying glass and take a very good looksee at both edges of the rubber.

 

My vote is inner axle seal.

 

That’s not a thing. There is a pinion seal and two axle seals, one at each end of the housing that the wheel bearing retainer seals to. I suppose it’s possible for part of an outer seal to come apart and make its way down the tube, but that’s a decently long journey to end up at the drain and not be sucked up into something else like a bearing first.

 

Where is the inboard oil seal?

 

See link supplied in Post #9.

 

The piece in the photo doesn’t really resemble anything in the rear axle assembly. From what I can recall, I don’t believe the o-rings that go onto the end of the axle tube are squared off like the ring in the photo. They are round, IIRC. There are only 3 seals, 2 axle shaft seals and 1 pinion. Unlikely any part of the pinion seal could have broken off and made its way past the 2 pinion bearings and out the drain plug without being chopped up. Axle seal is more feasible but still unlikely.

My bet is on some sort of manufacturing debris that put a foreign part in there. I can’t think of anything else it would be.

Courtesy of @Jowett, here is the diagram for the locker. It looks sort of similar to the part on the bottom row, second from the left, but even then, that part looks metal. Hard to tell.



If all functions properly, I’d toss it and keep driving.

 

I’m probably being nitpicky. I’ve replaced the diffs and the axle bearings before so I’m familiar with what is where. There’s only one seal + an exterior o-ring per side. To me, “inboard” implied there’s something sealing at the diff itself, which of course there isn’t. Anyways, I don’t think the part in the photos looks anything like o-ring anyways so for that to get past the seal would indeed be one hell of a task.

 

It’s the inner hub assembly O ring directly behind the brakes.