Why Is My Front Diff Breather Venting Gear Oil?

I stopped at a rest stop, and noticed spray on the rear tires. Then noticed spray all over the undercarriage. Traced it to the front, was a steady drip coming off the steering rack. Smelled it - gear oil. Best I can tell, the source is the breather vent, right up at the cap next to the transmission breather cap.

What's the deal? I had tried to change the front diff oil a couple months ago, but couldn't get the drain bolt out. But I stuck my finger in the fill hole and got no gear oil on it. I added oil until a little started to spill out, which I thought was how it should be when full.

Even though I hadn't noticed any leaking gear out the vent over the last couple months, I figured I must have overfilled it. Pulled the fill plug again this morning. No oil running out. Plug doesn't even seem wet.

Any ideas? I don't get it. It doesn't leak when parked. Seems to only leak when driving. Maybe it's even done leaking now. I cleaned things as best I could so hopefully I'll be able to tell if it leaks more.

I don't remember off-hand what fluid I used except that I did my research and used the correct viscosity. Some random part store brand, but the correct weight. If the breather was clogged it wouldn't be letting oil through, so it must be clear. I don't know what could be causing that kind of pressure. It's been colder lately than the last few times I drove the truck.

 

I don't know the answer, but I wouldn't put random gear oil in my front dif, they're expensive and hard to come by. If the manual says GL-5, you need oil that "meets specifications", not some "recommended for GL-5" garbage.

 

You'll need to make sure your vent is clean and functioning. I have taken them apart with success in the past but usually if they are plugged you can find success with a cleaner of your choice once removed. I think the front diff is the one closest to the firewall IIRC.

 

Alright, thanks. I have the Lexus drain and fill bolts ready, just haven't gotten motivated to do the work to get the current drain bolt out. It's right on the edge...I stopped before I completely messed up the recessed hole, but it's almost worthless. I should get back in there before winter really hits.

I'll get some Red Line GL-5. It's what I've got in the transfer case and what I used in the past on my Tacoma. I did find one thread on Taco World on the same issue, but most responses were about similar issues after putting in new gears, or a locking front diff, or incorrect fluid.

I did trace the vent to make sure I had the right one. Tight space in there...but I'll get it. I did figure after so much gear oil blowing through it, it could use a cleaning.

 

I was concerned about mine also after reading horror stories on here, then someone mentioned down inside the Allen hole, there's an additional smaller torx-head provision. Not sure if the earlier years have it also. But mine appeared to.

But I used THESE which (maybe it's purely imagination) seem to offer up more grip in the hole. Slap it into a smaller impact so you can put your weight behind it and within a few taps it should come free.

Of course, if you haven't hit it w/penetrant yet, maybe you should.

 

Oh interesting. I'll look when I get back in there.

Those look like they could be better. Since I hope to only have to do this once more before swapping the Lexus bolts in, I'm going to avoid the expense though. I'll start spraying penetrant now, and also have heat ready. Hopefully I won't actually need to use the cold chisel...but we'll see.

 

If you have any socket-based Allen heads, even if they're not fluted like the ones I linked, I highly, higly recommend using them. You'll get more directed torque, the hockey-stick wrenches tend to twist under torque and slip out, leading to deforming the hole in your fastener.

I can't remember if I already shipped my bag of old ones to another forum member or not. But I have (or had) a zip-top bag of about 2-3 dozen of the 3/8" drive and maybe larger/smaller ones in the shop I was never going to use. I can look if I still have them and ship to you for the cost of postage if I do. I like to pay forward my old tools where it makes sense. EDIT: Just ran to the shop. I'm not seeing the bag, I must've given them away already

 

I appreciate it anyway! I do use allen heads that clip into my socket wrench. Someone just really torqued down on the drain bolt, years ago, and there it's been, waiting for the next sucker to come along and try to break it free.

Once I get it out, I'll use the Lexus bolts and never need to worry about the allen heads again.

 

Searching the forums seems the most likely causes are overservicing, use of 75W-140 in cold climes, use of an additive that foams when churned. You might try using

$39 75W-90 GL-5 Limited Slip, Ultra Long Drain 500k Miles, Manual Transmission, Gear/Differential Lubricant (1 Gallon)

75W-90 and add the breather extender mod if your truck doesn’t have it.

 

Thanks. I've got Red Line 75w90 GL5 ordered, though I just looked and the parts store stuff I used earlier is also GL5 75w90. But the fact that I filled it months ago and only just noticed overflow once it got cold makes me wonder.

This is the front diff, so it's already got the OEM vent tube. I think it's just the rear diff that people add breather extensions to, right?

 

I forget when Toyota start adding breather tubes. Some of my older Hilux trucks didn’t have them.

 

Ok. How old are you talking? I don't remember now, but I wonder if the change came with IFS? Or did you have some IFS trucks without an extender? I honestly can't remember if my 98, 95 or earlier trucks had one. I know my 83 solid front axle didn't.

 

Agreed on cold as the possbility if that is when it started.

https://www.tundras.com/threads/front-diff-oil-coming-from-breathers.136363/#post-3451792

 

Lookin like, thanks for adding more weight to this theory. After my drive home (~120 miles on the interstate), there was no more dripping oil. It was also warmer out...maybe it'll overflow again when it gets colder, maybe the fluid level is low enough now that it's done leaking. I don't know. I've got gear oil on the way and I'll get it in there as soon as it shows up. We'll see.

I'm feeling a lot more comfortable with it now. But I'm sure you all know the feeling. Stop at a highway rest stop, see oil spray underneath the truck...crouch down, see an active drip drip drip coming off the front frame crossmember...think "should I call a tow truck? Crap!". Luckily I know what GL5 smells like, and it was easy to trace. At first I was afraid my steering rack had suddenly sprung a crazy leak, since the drip was coming off it.

 

Don't feel bad, you've successfully treated your frame for the season.

 

Part of it. Still need to buy lanolin spray.

 

Yes. Valve cover leaks can be deceiving too as they drip on other things. Haven't done it but breather relocation might help if it lengthened the tube. Seen others put it up on firewall. Also, once it's done getting oily might want to remove and clean it out. If it plugs then can blow the seals.

 

Figured id ask, but did you add the quantity per fsm. Easy to overfill a hair if not on perfectly level ground. Just for reference I overfilled s2000 by .2ths of quart and it burped it out breather after rainy road drift session. I thought I blew my tiny diff up.

 

If you strip it out like I did, Irwin makes a nice hex extractor set that works great. It can be frustrating to get those bolts out.

 

I almost certainly overfilled. Level ground doesn't exist at my place. Gravel/dirt parking lot, potholes, uneven. Considering it only takes a little over a quart...I don't remember how much I put in but it was almost a full quart before it started dribbling out the fill hole.

 

That's great to know. Hopefully I don't need it, but we'll see. I still got the fill bolt out no problem the other day, but haven't tried the drain bolt again since the first time. I think my gear oil will be here early next week.