I think it's a transfer case component, but not sure. PICS

[roboman]

1999 4.0 SOHC with automatic 4x4

There's been a slow, constant drip on the driveway under the hood area for the last two months and if it were summer, I would've crawled under right away, but I didn't so I finally checked it out last week since the weather warmed a bit. The drips on the cement were dark brown and smelled like motor oil, so when I crawled under, I was looking all over the block with no avail. Then I found a trail of wet grease along a silver unit. I don't quite know what it is though, but it looks like something involved with the 4x4 linking the front wheels. Or is it the differential? I'm a newbie so cut me some slack.

Taken behind the RF wheel:

Also behind the RF wheel; zoomed on the link between the silver unit and a drive shaft (which you can see has oil on it too):

In front of the RF wheel, taken under the bumper:

Oh, and maybe it's worth mentioning that a year ago, I had very similar drips but needed the oil changed within a week so I had them check it out. They said the pinion steering fluid was filled WAY past the proper fill level, thus was oozing through the cap. They drained it down to the right level, and no more drips.

 

[albi1cnobi1]

That is your front axle differential. That is where the drive shaft power gets split to both of the front wheels. It's hard to tell from the pics where the leak is coming from. It kind of looks like its coming from the diff cover gasket. If you can check to see if the top of the diff is dry. If it is its probably the gasket leaking. If its wet on top it could be from the engine dripping down. Gear oil has a very distinct smell. It is much stronger than motor oil. Check these things out and let us know what you find. Good luck, and we're all counting on you.

 

[Joe Dirt]

Looks to me like the pinion seal is leaking...

 

[albi1cnobi1]

I thought that might be it , but it looks like its wet on the front and maybe running back? Or it could be the pinion seal and its running forward when its sitting.

 

[Joe Dirt]

I only say pinion seal since it's higher on the case...

 

[roboman]

My driveway has a decent incline, so that's another variable since that means gravity is messing with how the fluid runs. And I just got home to check this, so I'll go run out to the garage and check those indicators out.

 

[roboman]

Ok here's what I gathered. I ran my hand over all parts of the differential, and visually checked what I could as well. There was no fluid on any part of the top that I could feel, and I didn't visually see anything along any parts of the side. Looking as far above it as I could, I couldn't see any dripping coming from above either.

Now for that bottom lip running north and south that has greasy crud all over. The clearest sample of the fluid sure looks like it's coming from that zoomed in picture (second pic) where the differential meets the drive shaft, and it makes a trail all the way to the front of the vehicle. The vehicle is parked on the driveway for 2/3 of the day, and the other third is in a flat parking lot, so that could explain why the whole lip of that thing is covered since gravity messes with it. Now, if you look straight up underneath that circular joint, around the innards of the connection you can see clean, shiny fluid. I don't know what color diff fluid is, so I couldn't tell you if that's what it is though. I did a smell-sample of what was dripping too. Once again, I haven't even spent much time around engine oil, but perhaps the smell is a little different, except I wouldn't say night and day. It kind of reminded me of outboard motor gear lube that my dad used to use in our fishing boat, if that's similar to diff fluid.

Now, I kind of settled on figuring it came where the shaft meets the differential as opposed to the front of it. On the front lip (in the third picture - where there are 2 bolts) there ARE drips, but they're only in the center where that north and south lip meets it, so while I wouldn't rule it out, I don't think it's coming from the front.

 

[Mike Draper]

It looks like the pinion seal. If it's been leaking that long I would pull the plug on the front diff and make sure it's full of lube....it'll save you some money in the long run, keep it topped off until you get the leak fixed...or don't use 4x4. I would spray it down with brake cleaner and wipe clean, do a short drive and crawl back under to confirm where the grease is coming from. There is a vent on top of the differential, make sure it's not plugged, sometimes that will cause seals to leak.

 

[roboman]

I thought I saw a plug on the driver's side... was that the one you're talking about. Also, it's tough to avoid using 4x4 because winter isn't finished here and I only have 4x4 auto, high, and low - so it's either auto or full time Any idea how much it would cost to have a mechanic work on that, or would it be doable for the DIYer?

 

[my pos mounty]

Looks to me like the pinion seal is leaking...

Me 2.
Keep it full, whether or not you use 4 wheel drive. It spins all the time your truck moves, so if it goes too low it WILL overheat and eat all the bearings within. Been there, no fun.

 

[my pos mounty]

You might be able to pull this repair off yourself. You will have to take the front driveshaft off, remove that yoke from the diff, replace the seal and put it all back together. COUNT how many revolutions it takes to get the nut off and do exactly the same number upon re-installation. Some guys have reported that this method worked for them.

The plug you saw was the one you need to remove (looks like a square head, insert a 3/8 extension) to add and to check the diff fluid.
To make it a heck of alot easier to add fluid, go to any GOOD parts store and look for what appears to be a greasegun, but the "business" end has a 3/8 hose instead of the typical grease hose. It will suck diff fluid into itself and you can push the fluid into that hole. Easier than any other way.

 

[roboman]

Ok so a few questions.

How much fluid is actually in the reservoir? Just so I know how much to buy, and also to estimate how much has been lost.

I would really like to try this myself since it would be neat to be able to conquer, but I don't have the time and there are a LOT of risks if I mess something up. Any idea how much it would be to have a shop take care of it? I imagine it would mostly just be labor, but perhaps not all that much if they know what they're doing.

 

[albi1cnobi1]

You're right, it will be mostly labor. The pinion seal is an inexpensive part probably under $20. I always encourage people to try to fix things themselves but if you're not that mech. inclined and can't have the truck down than check out a few shops and get estimates. It really shouldn't be that much, it only involves dropping the drive shaft and pulling the yoke off. Any good shop has seal pullers and its not that big of a job. But if you're feeling dangerous go to the auto supply, rent the seal puller pick up a new seal and have at it. Worst case scenario you can't get it out, you pull the front shaft and limp to the shop and grovel. Oh yeah, if I remember the front diff holds about 2 Qts. You fill it just until fluid starts to come out of the fill hole.

 

[roboman]

I really would like to try this, but I guess I'm just too chicken haha. This would by far be the biggest mechanical fix I've ever done. I have a friend that might be able to help, but that won't be for awhile so it looks like I'm going to just prolong the bleeding and refill the fluid for now.

Now I'm looking at my manual for the proper fluid type. I have the 4.0 SOHC with a 4.10:1 limited slip axle. It says that for LS models, you have to use synthetic. It says that concerning the rear though. Does LS mean I need synthetic for the front too? The synthetic it wants me to use is a different weight, which is another reason I want to get this right. And any brand preference to the fluid? Would there be a definite advantage of using perhaps Lucas Oil over Valvoline, or any other brand?

I really appreciate the help you guys have been giving me. Hopefully I'm not too much of a pain to deal with.

 

[albi1cnobi1]

You would use regular gear oil up front. There is no LS in the front diff. Use 80W-90, any good brand(Penzoil, Castrol, what ever your preference). Since you're just topping it off you have to stay with the same type. If you were draining and re-filling you could switch to a synthetic.I personally prefer synthetic but thats just 1 opinion, there are people on both sides of that fence. Good luck and keep us posted.

 

[Joe Dirt]

Robo- where in Michigan are you?

 

[roboman]

Joe - middle of the mitten, pretty much.