Hi everyone. I had my rear axle fluid changed in December and the pinion seal replaced in January. 2 months later, it looked like it was still seeping, so I wiped it off to see if it was leaking and took it back to the same shop. I told them that I wiped it to see if it was still leaking, but they said it was not leaking for a fact and whatever was still there is old (just a little). They said if it was leaking any fluid it would be all over the place since I drove it 35-40 miles to get to that shop. I think they said the fluid was full. Just now, I checked it out and the bottom of the axle was damp again but not dripping. I wiped it off and smelled it. I can't tell if it is gear oil or not, but it is dark. My front axle leaks for a fact and I always have to top it off every few weeks (I can't find the source), so I know what gear oil smells like and it isn't pleasant. Do pinion seals just start leaking like that at random when it was just replaced? This is a 4x4 shop that replaced it and I don't think they could have screwed it up. Do those seals just burst at random if I don't have it fixed?

EDIT: Could this be engine oil blown back to the back of the car from high speeds? I found that to be the case with the transmission pan and I know my trans does not leak (fluid is red, always was because I have it changed every 15k). I am finding old, dried oil throughout the undercarriage. I know I have an oil leak and the oil pan is covered in oil. The paper towel looks and smells like oil, but it seems like it is a different type of oil compared to gear oil. The place on the diff where I am talking about is just below the driveshaft to about 3 inches back.

EDIT 2: I looked again and found brown oil residue from the oil pan, to the transmission (bell housing and pan (top to bottom and 2/3 of the bottom surface of it is brown oil)), to both of the front surfaces of the cross members (T-case is clean) at the trans and T-case. I took 2 yellow drops on a paper towel from the front diff leak and I could not stand the smell. With my nose an inch away, I could tell it is gear oil. The brown oily residue from the rear axle is almost odorless and I can't really tell for certain if it has the same smell as the gear oil. I literally stuck my nose in it and all I could smell was the paper towel itself, but not really the oil. Could this just be blowback from the front of the car? I will check the oil level in the rear axle within the next couple days when I get ramps to do my engine oil change. How much gear oil is really needed for it to smell bad? A whole drop or just oily residue on the outside of the case?

 

Go for a drive, get the lube up to operating temp, park it, clean up the rear with brake cleaner, if your rear is topped off with gear lube, & you can leave it sit a day or 2 you'll know.

 

I shall do that. However, I cannot tell how much fluid is really in there. The fill plug is rusted from the winter and I cannot get it open. I bought some PB Blaster and a 1/2"-20 plug from Advance and I will check it out tomorrow. However, I am beginning to think it is something else. I wiped it last night, drove it around town today and there is no more accumulating on there (or at least none that I could wipe off). I noticed that the oily residue was just after I drove it on the highway for 50 miles each way. Maybe it could be engine oil? It doesn't have the distinctive smell of gear oil like the front axle that I have to keep topped up every few weeks.