Hey all! It's not often I get to come in and ask a question, but I'm hoping someone can shed some light on this one...

My wife's DD has 100k miles, all stock, owned since 18k miles. Recently, I noticed a little seepage from the rear diff.

This truck is pristine underneath, has always been babied and pampered (it rarely sees 3500 rpm, never been off-road, never been in 4WD, never towed, never exceeds 65mph).

Removed the diff cover to re-seal it. Cleaned and bead-blasted the cover, followed all the factory specs (RTV, fluid, torque) and reinstalled. Leaked a day later.

OK, maybe I did something wrong. Removed again, cleaned the cover, checked for flatness on a granite machinist's slab, re-sealed, refilled, leaked the next day.



At this point, I can only surmise that it's a failed diff vent / axle vent. Pulled up all of the articles on axle vent mods (common for the Frontier and Titan), as well as all the factory exploded view diagrams. NO vent to be found. I inspected every inch of the rear axle and diff. OK, that's odd - Dana 44 HAS to have a vent (little jiggle-cap bastard that gets clogged up). NOPE.

What I DID find was a tiny square plug on the passenger side axle, around the 2:00 position (if looking at the right rear wheel). It unthreaded easily, and it's about 1/4" NPT, made of black plastic.

I replaced the plug with a 1/4" fitting, attached a 2' length of spare tubing, ziptied it up into a cavity behind the bumper facing down (so as not to collect dust), and it's been a week with no leaks. I win.

NOW, with all that said, what do you guys think? Was this an oversight at Nissan during assembly? How has it not blown the axle seals? What's the black plastic plug? I'm eager to hear if anyone else is aware of this, or if our truck is an anomaly.

Thanks in advance!

I've combed through everything I could find and even asked a DTS and a few people upstairs, nobody seems to have a clue why there's no vent. I can confirm that there isn't one, either on the C200 or M226 variants. I can only presume that engineering decided the fluid levels and expected operating temperatures didn't require one. There doesn't even seem to be a p/n for the plastic plug.

My DTS basically shrugged and said, "If it needs one and he made one for it, it can't hurt." So your guess is as good as ours.

Weird. Thanks amigo. I'm amazed we weren't popping axle seals, but fixed is fixed!

Yep, all's well that ends well. Forgot to mention, this seems to go way back. We had an '06, '07 and '11 on the back lot and there was no sign of a vent on any of them. I suppose if the seals are all double-lipped then maybe it's designed to hold some amount of pressure or vacuum.

One would think the axle seals would go before the diff seal. But, all's good.

Next up is the fuel filler venting issue.

If it's difficult to fill, there's a bulletin about it for just about everything Nissan between '04~'15, NTB17-030:

https://static.nhtsa.gov/odi/tsbs/2017/ ... 4-9999.pdf

Basically look for a blockage in the vent tube between the evap canister and fuel tank, or a stopped-up canister (probably flooded). If neither of those are bad, there's an ORVR (Onboard Refueling Vapor Recovery) valve built into the fuel tank that can stick. It discharges through the evap vent hose, so the easy way to test it is have an assistant pump some fuel into it with the vent hose disconnected at the canister. If the hose is open but no air comes out, then the ORVR is stuck or clogged.

You rock amigo. Love and beers from the Ranch.

AZhitman wrote: ↑

Thu May 06, 2021 9:57 pm

You rock amigo. Love and beers from the Ranch.

Always happy to help, my friend. You rock pretty good yourself.

Just reading through that TSB (admittedly late, everything's a project here lately).... Looks like the emissions coverage may still be in effect on our rig. Gonna drop it off Tuesday and let someone else figure it out. It's too goddamn hot here to be covered in fuel and sweat.

So, per the dealer, it's not the vent tube. It's the valve in the tank, which means tank R&R.

I think we'll leave it be, since it's not consistently a PITA.