Rear pinion seal, or worse?

Hey all, first help thread. I have a 2009 DCLB OR with 170k. I’ve had it for the last ~3k. Was recently under it and noticed a bunch of buildup near the rear diff and gas tank. It’s definitely some sort of oil, and the stuff on the tank looks like it has that foamy look like it’s got water mixed into it. It looks like it has been slung in a pretty perfect line on anything above and around where the drive shaft meets the diff, which some digging suggests a rear pinion failure, but none of the prior threads have any photos that look like quite this much stuff so I’m worried there might be something worse (or just a worse failure). It’s also strange to me that there isn’t actually any noticeable buildup right at the diff and where the shaft meets.

Any ideas? I tried to take some pics, but difficult without lifting the truck. Hopefully you get the gist.

For what it’s worth, I recently (a week or so ago) replaced the old and shot (but not stock, some shitty Moog stuff) front coil overs and rear shocks with 2022 TRD OR takeoffs. This raised the front of the truck about 2” and the back maybe a smidge. Not sure if that could possibly be relevant, but worth throwing out there. It looks to already have the TSB rear leafs installed somewhat recently.

 

The “slinging around” effect makes it quite likely that it’s grease slung away from the u-joint after being greased up. Your differential is too dry for it to be coming from there. Check around the other U joints, see if you see more or less the same thing.

The amount on the gas tank is more than I’d expect, but perhaps it just indicates there was a lot of grease tossed about over the years.

 

Thanks for this, it definitely seems like grease sling similar to what I see when a CV boot goes out. Good to know about the diff, makes me feel a bit better and is consistent with not noticing any residue immediately on that seal area. Will check around the other joints and report back with anything more unusual.

 

Diff seal looks fine, and ujoints don’t appear to have been slinging much grease. I’d clean it up and see if it reappears. Looks lien a pinhole leak in your tank to be honest. Does the fluid on the outside of the tank smell of gas?

 

Yeah the u-joint itself doesn’t look wet, and this stuff seems fairly new and “wet”, so it’s a bit confusing. The pattern (hard to see with my pics) definitely looks grease sling-like, just hard to say from where.

It does have a smell, but not like gas, definitely more oil or grease. That’s honestly the very first thing I thought when I spotted it and I immediately smelled it. I’ll try to clean it up and see what happens. Thanks.


The other potentially odd thing is the warping of that rubber strap thing on the tank. The one at the other end isn’t warped like that, which almost makes me think this one is getting really hot or something.

 

This. Mine looks very similar after greasing the zircs on the u-joint, any of the old grease that is pushed out get slung out in the same pattern if it’s not cleaned off good enough