Ok, so I dropped the tank and replace the fuel pressure regulator on my 99 Sahara which fixed my slow starting problems. But when I had the tank off I noticed that there was some grease on my axle to the left of the differential (just under where the vent hose connects). I didn't think much about it at the time because I was more concerned getting the pressure regulator installed and seeing if that fixed my fuel system problems.

But now that that's fixed, I'm wondering if this grease is a serious problem. It seems to be coming from the top of the axle where the vent hose connects and is spreading down and around to the bottom of the axle. Or could it be leaking around the axle where it connects to the differential?? It doesn't drip on the ground yet. I cleaned the axle off so I can see how quickly it reappears. I wish I would have looked more closely when the tank was off so I could see better.

My Sahara is a 1999 with 68,000 miles and very little off-roading unless you consider MN winters as off-roading. And the rear axle is a Dana 44.

Sorry to get so long winded but I just went out and looked at the problem from front side and the leak is definitely coming from the area where the vent hose connects to the axle but it appears that my brake lines connect to that same point--a little rectangular piece of metal on the top of the axle with the vent hose coming in the top and brake lines out the sides??? Now I don't know if my vent hose is leaking or if it's brake fluid. Once it leaks some more I'll see if it smells like brake fluid. Any helpful ideas? Stupid question, but why do the brake lines hook onto the axle?

Thanks.

Is it grease or gear oil?

Sorry, I guess I was kinda vague. I think it's more like oil but it's been there for a while so it's pretty thick and full of road grime on the top. Toward the bottom of the axle where it ran, it's more like a charcol colored oil. I assume the color is from the dirt.

Brake fluid? The rear brake block is there as well.

If its gear oil, your vent hose might be clogged. There should be a cap on the end of the hose also, it is a vent cap and that might be bad or clogged also. In any enclosed structure with moving parts and fluid you will get splash and preasure build up. If the vent is plugged you might even get seal leaks on the axle seals. Some seapage is normal if the hose doesn't have a good enough seal or the axle was over filled at one time, but it is good to check the hose anyway. I would tell you a trick we use to use in the shops about tasting the fluid to see what kind it is but I think that messed me up over the years. Gear oil stinks badly. With the description you gave it sounds like gear oil to me. Best bet is blow air through the hose while its pointed away from you and if you have a cap on it soak the cap in water with dawn dish soap in it. After soaking for about 30 to 45 minutes run fresh water through it, Make sure the cap is clean of all soap and debris before putting it back on. Some of the caps have small slots in them, these are the better ones but some are spring loaded and any dirt or road grime in them causes them to clog.
As far as the brake line block it is a hard part, they can leak over time especially with vibration, You can try to tighten the lines and examine the block for any cracks. If the brake line block is leaking enough you will get brake fade on the pedal. Being it is on the rear you will only notice it slightly. Brake fade is when you are at a stop with the brakes fully applied at a normal braking preasure, your pedal will slowly move to the floor, being in the rear it will be very slight and hard to notice.

Hope this helps, I use to hate working with axles not only did my Fiance stay away from me but even my Beagle hated the smell of the gear oil.

Thanks Odhinn for the useful suggestions. I'm going to check the vent hose. The plug on the top looked pretty clean when I worked with it the other day but I'll pull the hose off and check just to be sure.

Since I cleaned the area two days ago it doesn't seem to be seeping so it probably isn't a major leak. Probably been accumulating for many years. It's only visible from the back or if you look at the top side of the axle. Usually when I change oil, I'm looking for any leaks up front.

I'm probably just paranoid about little problems because winter is approaching and it is NO fun to be working under the Jeep when it's 10 below outside. Even in a heated garage everything melts and drips salt, sand, and freezing cold water on you. Gotta love Minnesota.

Thanks again for the help!

No problem at all. If it hasnt returned after the cleaning then it is prabably just seepage from around the hose. Yep i know MN Winters lol after being down here for over 10 years I wanna come back.