tardman91

Well, just when I finally think I've solved my power steering leak, I find something else. Took a trip this wekend and the truck did fine. About 200 miles or so on the highway.
Came home from work today (the truck sat in the garage all day) and noticed some oil on the floor near the rear diff. I checked it out and it seems like maybe it's leaking from the top? There's a hose that goes in there (what for, I don't know) but it looks like it's wet up there. While I was under there looking around I noticed a bunch of crap that looked splattered over the undercarriage. It's kind of dark, so it doesn't seem too fresh, but it was greasy and dirty. Any idea what the heck this could be? And do you think they're related? And what's that tube that runs into the top of the rear diff and could that be the leak? I feel a visit to my mechanic coming this week. Dang.

toyota4x4907

There are quite a few tubes running to the rear axle- brakes, parking brake,...but What you are describing most likely is the ABS sensor. Any pictures?

Looks like you might have a ruptured brake line....

corax

your pics look like the transfer case output seal is just flinging a little bit of gear lube around. Mine's been doing that ever since I bought it, though it is on the list of things to take care of eventually.

What year/model truck do you have? The hose going to the top of the rear diff is quite likely the brake line if it goes into a "T" with one hose going to each drum brake.

tardman91

It's a 94 4Runner auto with the 3.0.
So the gunk that's splattered on the undercarriage probably isn't that big a deal? But whatever is leaking from the rear diff probably should be looked at ASAP? I'll go snap some pictures.

justin_4runner

does it smell at all? it doesn't look like its coming from the drive shaft but the tube leaking and air moving it around, could be coolant from the rear heater. those look like the pipes for the rear heater.

tardman91

Can't be the rear heat because I don't have it.
Here's the diff. Looks wet around the bolt, but feels dry to the touch. It drips from the bottom. I'm certainly no mechanic, so I don't really know.

tardman91

Here's the other side. Looks wet on the top, but again I'm no mechanic. You can see where its leaking on the bottom. Maybe it's the seal between those bolts? Is that the rear main?

Moonfish

It looks like the pinion seal is leaking in the last picture. Follow the wet spot forward until you find the problem. When you're driving the oil leaks and blows back.

justin_4runner

the fluid is more up front where its leaking, up by the transfer case, and its getting blow back there, no thats not the rear main seal, rear main seal is the seal on the back of the motor on the crank area, it could be the rear tranny seal, but it would have a little more red color to it. does it have any color at all to it?

toyota4x4907

Looks like its leaking from the pinion seal (between driveshaft and diff) and from the ABS sensor (tube attatchemnt on top.)

tardman91

The stuff up front is a little reddish. The stuff dripping in the back is more brown. At least seals aren't that expensive, right? How about the labor? Would you say I might be looking at a couple hundred bucks to get them replaced? Hopefully...

justin_4runner

yeah just do a rear seal on the trans and have it flushed and serviced, if u havent on a while. and then drain seal and refill on the rear, 20 to 300 labor and 40 in parts all fluids included

tardman91

Ok. Did a little more investigating and have made a few observations.
There are 2 spots where the splatter seems to be concentrated and they're at both ends of the driveshaft. So the one up front (rear tranny seal? The fluid is brownish-red) seems to be leaking slightly and getting flung all over.
The one in the rear (did someone say that's the pinion seal? The fluid there is dark, almost like used motor oil) it's leaking from between the driveshaft and the diff, and dripping back to the bottom of the diff and falling from there. That explains the splatter on the side of the gas tank directly next to that spot.
Does this make sense and sound like a common-type problem?
If it does... Any ideas of what I might be looking at cost wise? I have a mechanic that's a friend of my brothers and he's always been honest with me (as far as i know) and cuts me breaks on prices, but it's nice to at least have an idea.

jeetS

the tube that runs into the rear diff would be the diff breather wouldnt it?

toyota4x4907

Yeah, both those seals are pretty common failures. The reddish from the front one will be because of your ATF. The rear, because of the gear oil (brownish)
Price varies. Parts are cheap. Make sure he knows what he his doing with the rear pinion seal.

No. No factory "tube" for the breather, just the 1/2" valve cover. Definitely the ABS sensor. Look in the last picture. You can see the ABS sensor between the anti-sway bar hoop and the diff. The diff breather is the nipple thing off to the right.

tardman91

Ok. I guess my highway driving this weekend aggrevated the leaking a little making it more noticable. This is the first time I've seen the rear drip. I've never seen the middle drip before, so it must be a really small drip that just gets splattered everywhere. I checked the trans fluid and it's not low. If anything it seemed a bit high, but I measured it when the truck was hot. Definitely NOT low though, so that's good.

Mine looks a little wet up there, but I'm not concerned about that. I'm not getting an ABS light or anyhting and the brake fluid is perfectly topped off. It's probably just some of that wild gear oil that's flying around in that area.

toyota4x4907

Yeah, a little amount of gear oil can make a huge mess when its flung from a rotating mass going a few thousand RPM. You probably arent leaking brake fluid from the ABS sensor, but gear oil is probably leaking from the seal at the diff to sensor. Pretty common reason why the pinion seal and ABS sensor seal leak is from a clogged diff breather. Lots of people, including myself, have cleaned or gotten a new breather and the seal stopped leaking. I did have to replace the pinion seal, but it started leaking this past winter again so I cleaned the breather and it hasnt leaked since.
Also, since both ends of the d-shaft are leaking, you might want to have your U-joints checked out. Another common reason of leak is due to d-shaft vibrations. Are there any vibrations while driving?

tardman91

I don't really notice a vibration. There must be a slight one (that I can't really feel) that causes the 4WD shifter to make noise. If I touch it the noise stops. I figured a little bit of vibration was probably par for the course for a 17 year old vehicle with 176k miles. I just really want to get the leaking taken care of because it makes the occasional mess. I'm stopping by the mechanics' after work.

Also, how can I check the diff breather? It's that little nub to the right in that last picture, correct? Does making sure it's not clogged involve taking anything major apart?

toyota4x4907

Have him check the U-joints and the balance of the d-shaft. Could just be that both seals started to leak from old age, but seems too much of a coincidence

Honestly, I dont think its from your diff breather. Your axle looks super clean. Doesnt look off-roaded. But you never know. First, just see if the "cover" isnt sealed shut by grime. Just take a hold of it and twist it. Then see if it has any up and down movement. Really only a few mms is needed. Then, you can take the valve out completely. Its just like a hose fitting/adapter type thing. Hole through the inside, threaded on one end with the "cover" being the "valve", and a hex section to fit a wrench around it. Its just so the differential doesnt build up pressure due to the expansion of the hot fluids and air in the differential.

tardman91

Gotcha. I'll see what the mechanic thinks this afternoon. This truck just keeps costing me $$. Not that much really, a little less than $1500 (including a set of 4 new 31" tires) since I bought it. I just gotta keep telling myself "It's paid for, and there's $10,000 in the bank so my wife can get her masters' degree." I love my 4Runner, but it's stuff like this that makes me miss my F150.