Leaking Axle Housing/Differential Breather

I have a Meritor rear-end that is leaking fluid out the breather. A little back ground.....A few days ago I noticed the cap (pop cap style) on top of the breather had came off on my front drive axle. I got a new one from the dealer and installed it. As a precautionary measure I drained some oil off to make sure it wasn't contaminated. Refilled the differential to the top of the fill hole. Oil that I drained off looked good, not contaminated and no water present. Yesterday I did a local run which took me approximately 65 miles one way. When I got to my drop I smelled gear oil but upon inspection couldn't find any issue. Today I picked up another load and before I leave my loading/unloading point I always inspect everything to make sure it is okay. This is when i realized there was an issue. I found oil dripping off the axle housing. After looking around I determined that it is spewing out the breather that I just replaced. My first thoughts were there is something causing the fluid to get hot (bad bearing). I called a heavy mechanic friend of mine and asked him what he thought and he thought the same thing I did. Oil is getting too hot. But both of us thought that even if the oil got hot it wouldnt expand that much, because really you are only filling your axle housing up 50% before it reaches the full mark. It doesnt make sense. I end up taking the load back off the truck because I didnt want to get under way and have something happen and delay delivery of the load. I drove back to the yard which is about 1 1/2 hours away. As soon as I got back I got my infrared temperature gun and took the temp on both axles in a few places they are both reading about 80-85 degrees. I am unsure what has caused my issue, any ideas. Tomorrow morning I am also going to take and swap the old breather on the other axle with this new style breather to see if I still have the same problem. (see pic below for new style breather). My old breather doesnt have this elbow tube on the bottom. After I swap breathers I will refill the differential, which is about an inch below the full mark right now, and I will take it for a drive up the interstate to see if I can duplicate the spewing fluid issue I am having.
Thanks in advance for your input.

 

I wondered about this. That is one of the reasons I decided that I would swap the old breather on my other axle with the new one to see if that would solve the issue. Well if that is the case if I put the new breather on my other axle it should start spewing oil from that axle. I will know tomorrow because I am going to give it a whirl.

 

Okay, so here is an update for my issue. I took the new breather out of my front axle and installed it on the back axle. I took the old style breather off the back axle and installed it on the front axle. Doing this swap would tell me if it was an axle issue or a breather issue that I was experiencing. When I installed the new style breather (pictured above in my first post) I orientated it the same way it was positioned when installed in the front axle. In other words, the opening in the 90 degree elbow tube was pointed towards the gears. I took the truck on a test drive after swapping the breathers around. Halfway into the test drive I stopped to check everything out. The back axle (which is where the new breather is now installed) is now spewing oil. Turns out the way the breather tube was positioned in the axle housing the gears were throwing oil into the tube at such velocity that it was causing it to spew out the breather. I turned the breather 180 degrees so the breather tube was now facing the axle housing, cleaned all the oil off with some brake cleaner and continued the test drive. The second half of the test drive went flawlessly and everything is leak free.

I really thought my differential was toast. In approx 150 miles I lost 1 inch of fluid in my diff. I think it is a good idea for people to make others aware of the issue that I had, that way they don't have the same issue I had or worse lose a rear over a simple 30$ breather.

 

New style breather Meritor released. I actually thought about cutting the elbow off with a cutoff tool.