Really weird differential leak...pinhole in housing

[nissanman04]

About a month ago, I went to an auto-x event in Buffalo, which is about an hour drive for me. When I arrived, the back of the car was really dirty. It looked like carbon build up to me, I didn't think much of it at the time. I did all my runs and went home. When I got back, I wiped some of the "dirt" off with my finger. It felt like oil, and I smelled it and it was definitely gear oil. I get under the car and find the entire passenger side of the differential is completely soaked and dripping. OK, only one side is covered in oil, it's probably a leaky output shaft seal, right?

I ordered 2 new seals. Since I had the diff out anyway, I decided to replace both of them. When I pulled the output shaft out, the seal didn't seem excessively leaky, just a tiny bit of moisture here and there. I replaced the seals and put the diff back in. To test it out, I went for a test drive for around 20 minutes. When I got back, I obviously found the same soaked differential I had before. Well, there was only one more seal that could be leaking since the driver's side was bone dry and so was the cover gasket.

I ordered an new pinion seal and installed it (the nut was a real PITA to break loose btw). At least I didn't have to drop the entire differential this time. I went for another test drive and, you guessed it, the diff was completely soaked again. At this point I am super frustrated and don't know where to go next. I kept thinking that maybe I installed a seal wrong or something. For a moment, I did think of the possibility of a cracked housing, though it was highly unlikely.



I pulled the diff again today, just to take a closer look at what the problem could possibly be. If there was a crack in the housing, I should be able to see it if I shine a light inside, right? I pulled the cover off and shined a bright flashlight inside, but I couldn't see anything coming through. I resealed the cover just in case and cleaned up everything real good. Instead of going through the trouble of putting the diff back in and having the same thing happen again, I decided to fill up the diff all the way to the top and see if I could see where the oil was coming from. Sure enough, a nice stream comes dripping out the side of the housing. It turns out a pinhole had opened up in the casting. I drained out the excess oil, cleaned up the area real good with a wire brush and degreaser and patched the hole with jb weld. If this doesn't work, I'll just find a new housing, but at least I know exactly what the problem is now. This is one of the weirdest (and most frustrating to diagnose) failures I have come across when working with cars. I'm so glad it's over...I just want to be able to drive the car.

[nissanman04]

well I thought it was interesting...

[Razi]

Interesting indeed.
I wonder how that got there.

[ZootedS13]

hit it with a spot of weld.

[nissanman04]

Interesting indeed.
I wonder how that got there.

Me too, I took a close look at the gears and everything looked perfect...I don't even know how long it was like that, since I haven't really driven the car too much.

hit it with a spot of weld.

I would if I had a welder, but if the jb weld doesn't work, I'm just getting a different housing. Open differentials are a dime a dozen.