Oil dripping from bottom of front diff

Just bought a '00 XJ w/176k miles. Had it since Saturday, looked it over as thoroughly as I could prior to purchase, and didn't notice any issues when I bought it (PO could've wiped it down first, though). I took it out this morning, and when I got home I noticed a plate-sized wet spot where it'd been previously parked. Looked under it where it sat, and sure enough there was a fresh spot of oil.

It's dripping from the bottom of the front diff and the shaft going into it from the back. It's sat since 11:00 this morning, and doesn't seem to be actively leaking as it sits. I have a picture, but I don't know how to add it to this post. The only option wants me to "enter the URL" of my image. ??? So, if anyone's willing to help with my main question, please let me know either a.) what additional details you'd like, or b.) how to post a pic. Thanks in advance!

Does it stink like sulfur? Or is it much less odiferous like motor oil? If it stinks it's gear oil from the differential. If the oil if coming from where the driveshaft goes into it, it is the pinion seal. If it is only at the bottom, it's more than likely the differential gasket. Both are very easy fixes with simple tools

1990JEEPXJ said:

Does it stink like sulfur? Or is it much less odiferous like motor oil? If it stinks it's gear oil from the differential. If the oil if coming from where the driveshaft goes into it, it is the pinion seal. If it is only at the bottom, it's more than likely the differential gasket. Both are very easy fixes with simple tools

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There's an odor, but I'm not sure I'd go so far as to call it sulfurous. Either way, the last line is what I was hoping to hear. I've probably got the tools and could YouTube my way through some maintenance, but I'm a noob and don't want to get myself in trouble. A trusted, retired mechanic offered to look the whole thing over on Monday, so I'm going to sit tight until then and let him take a closer look.

Thanks for the info!

yep, easy fix. congrats on the Jeep. they like to mark their territory!

denverd1 said:

yep, easy fix. congrats on the Jeep. they like to mark their territory!

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Thanks, but I've gotta admit that today has made me a little nervous. My guy's gonna help me do a complete flush/refill of all fluids, replace the valve cover gasket, and figure out what's going on with the oil around the diff. It MIGHT be coming from the VCG, but I have my doubts. Seems awfully damp/slick around the drive shaft/differential connection.

could be pinion seal. Those seem to go before diff cover seal. Also if it has the press in rubber plug those can dry out but I think those are only on the rear, the D30 IIRC still uses a real screw in plug. Am sure my D35 had a rubber one and *think* my 8.25 does as well (I know, I haven't spent enough time underneath it yet)

http://www.ebay.com/itm/15219890235...99&_trkparms=gh1g=I152198902354.N36.S1.R1.TR2

And a new seal.

Still can't post pics, so bear with me as I try to clarify (or further complicate) the issue:

When I parked this morning, there was a baseball-sized, dark stain beneath the front diff (looked like oil). Later this evening, I started it up, reversed about 10 feet, and in the time it took me to stop, put it in drive, and roll forward, the XJ had left a larger patch, and the fluid was much thinner and clearer - though still dirty and with a very greasy feel.

FWIW, it only seems to leak if it's running.

Check your power steering fluid.

I still can't quite put my finger on the larger, wetter spot. Just doesn't look like oil, but it feels greasy and looks dirty. And it has mostly dried since yesterday; still visible, but not nearly as dark. If I'd been using the A/C, I'd be fairly confident that it was just drainage, but the A/C isn't all that cool* so I haven't even used it in the few times that I've driven the vehicle.

I checked all the fluids, and other than the oil being just a little on the low side, everything else appears to be okay. Not sure if any of that changes anyone's opinion about what's going on, but just thought I'd throw it out there.

*The A/C isn't a huge concern since we're on the back end of summer, and I knew going in that a cold-blowing XJ is kind of a rare bird these days. I don't feel pressed to get that looked at any time soon, UNLESS it's either a.) a symptom of something more urgent, or b.) something that could eventually cause a bigger issue. Are either of those scenarios possible? And, when the time comes to fix the A/C, what's the most common process for tracking down the issue? Recharge it and see what happens, or do XJ owners typically have to replace the compressor?

AC: I'd check all the lines over first. pressurize the system with air and see if you find anything obvious before you dump refrigerant into it. may or may not need a compressor, depends on what went wrong to start with.

leaks: your Jeep is 17 years old, mine's 19. seals are starting to crack and dry rot and it just needs a little maintenance! nothing to worry about. check brake fluid level too. replace all fluids - will make it easier to track down when its fairly clean and smells like it should.

when I bought mine, I didn't have the time or knowledge to do something like a front pinion seal. Paid a shop to do it. Recently put a locker up front and had to laugh at myself at how easy the pinion seal job seemed just a few years later.

Pinion seal is easy. I'd buy that u bolt conversion linked ^^^. disconnect front shaft. remove yoke. remove seal. replace seal. put in u bolt yoke. attach front shaft. could be done in 15 minutes.

In left hand drive vehicles (NOT a postal right hadn't drive), the A/C drips on the passenger side. The differential case is on the drivers side. What you are describing is very likely the pinion seal mentioned earlier. I would verify nothing else is leaking though, like the power steering. The pinion seals typically leak either because there is slop in the pinion from worn bearings, worn seal, or worn yoke. It doesn't take a lot of wear on the yoke to make the seal leak. If you can feel a ridge with your fingernail the yoke should be replaced. You can do the u-bolt conversion if you want. The factory yoke is Spicer 2-4-6561-1. The factory seal is Spicer 44895.

UPDATE...

So there's no change in the condition of the seal leak (whichever seal it turns out to be). HOWEVER, I'm 99.9999999999999% certain I've identified the source of the larger spots of dirty, greasy fluid. Something is leaking from the rear left wheel: the source is either the axle or the brake line, but there was dark, slick fluid running through the tread of the tire, and the inside sidewall has dried fluid streaks all the way around the tire, running from near the bead to the tread. It's really slick and gunky where the axle meets the brake, so I'm not sure if what I'm seeing is seeping from the axle, itself, or from the brake. But, given the color, smell, and consistency of the fluid, I'm gonna guess it's brake fluid. Only thing in the axle would be much thicker grease, right? And it wouldn't run like that, would it?

Gear oil will do the same thing. You have to pull the tire and drum to see what's leaking. IF you were leaking enough brake fluid to cause streaks you'd probably feel it in the pedal, so its probably a rear axle seal.

md21722 said:

Gear oil will do the same thing. You have to pull the tire and drum to see what's leaking. IF you were leaking enough brake fluid to cause streaks you'd probably feel it in the pedal, so its probably a rear axle seal.

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Good point. Braking feels normal and effective to me, but who knows? Maybe the brake performance I'm feeling is suffering from a leak and I just don't know any better because it's the only way I've driven it.

Either way, thanks for the tip. Gives me a good idea where to look.

My dad (who's fairly competent in diagnosing mechanical issues) came over today to check out the XJ. I let him listen to it run for a few minutes, because in addition to what we've discussed in this thread, I've also noticed a slight, but consistent, abnormal sound in the motor. He seems to think a rocker arm, or something in that vicinity, might be sticking a little bit.

Now, I have absolutely nothing to base this on except paranoia and '00-'01 horror stories, but if he's right, is this an indication of the dreaded 0331 cracking issue? If I haven't done a very good job of explaining this, let me know and I'll provide as much additional information as I can.

No. My '99 sounded like a bucket of bolts but ran strong. Maybe a loose piston or something? who knows. Also check your flexplate bolts and shine a flashlight up in there to make sure the flexplate isn't cracked, and wiggle the evap solenoid on the pass side of the firewall (that can sound just like a bad rod bearing.)

If you have a cracked head, you'll have oily coolant, mayonnaisey oil, things like that. You won't hear noise unless/until it's been run that way for too long and you wipe out the bearings.

Your dad's guess is also a good one, and won't hurt anything if he's right. Just check the things I said, look at the condition of coolant and oil, and maybe change the oil and see how it goes from there. If everything is otherwise in good condition and the flexplate is OK, some fresh oil and an Italian tuneup might loosen a sticky valvetrain part.

The "standard" 0331 head crack occurs between the 3-4 rocker arms on the top of the head. It does not contaminate the coolant any noticeable amount, but it does cause the oil to be contaminated with coolant. It's about the easiest head crack to find, because you can remove the oil filler cap and look straight down and see if its leaking. Any visible coolant or coolant stains indicate the head is cracked.

Any of the other noises or sounds are probably unrelated to any potential head cracks.

If the head was cracked bad enough for long enough, you will be adding lots of coolant and have low oil pressure because coolant is corrosive to the bearings.

This has all been very helpful. Thanks to each of you for contributing. I'll have more info tomorrow if anyone's interested.