Oil leaking from vent after rear Zip locker/Gear install

[jeep.kevin]

Alright this is gonna be a long post.

A while back I have zip lockers and 4.88 gears installed in front and rear 44s for my MJ project. I just got it up and running and went through the break in process for the gears as my installer recommended (Robert @ Rwkhaussupply).

When I first filled the diffs up I put in the factory recommended amount of oil and they both puked oil, at the time I thought it was over serviced since its a full case locker. So I pulled out a half quart of oil and continued the break in.

After the break in I changed the oil and only put in 1.5 quarts. Only driving on surface roads to work every now n then the rear diff wasn't spitting out oil anymore so I thought the issue was resolved.

This weekend I took the MJ on its first wheeling trip that was about 150 miles round trip with mostly freeway there and back. I noticed some oil had come out the rear vent and made a mess. I drained the oil out today and I lost a half quart of fluid from the diff leaving only one quart remaining in the diff. If anyone has some advise I'd love to hear it.

Some things to consider to help me resolve this issue:

-I did a search prior to posting on here and know about the relief that needs to be made in the rear for better drain back (my installer mentioned this step). I couldn't find much about this specific locker only ARBs pretty much.

-Its a rear 44 from a 91 grand wagoneer

-I have the breather vent moved to the top of the diff cover since I put a truss on the axle and the stock breather hole is blocked off.

-I have a Ruffstuff diff cover installed

-It doesn't seem to be leaking air in the diff since the locker stays engaged and my compressor doesn't kick back on.

-I have about 3' of breather tube that leads high up into my bed.

-The pinion is rotated up a few degrees since I have a 5.5" lift and a SYE installed.

I contacted the installer as well but it's Sunday so I'm waiting to hear back from him. Anything helpful will be much appreciated.

 

[anthrax323]

Seems like having the vent installed in the diff cover would lead to the ring gear slinging oil directly at it. Isn't it typically on the driver side axle tube as part of the brake line splitter? I know on the D30 front it's in the pumpkin, but opposite the ring gear.

 

[jeep.kevin]

Correct, but since I put the truss on I had to move it. I had seen other people move their vents to the same spot when trusses were installed tho. It's not directly facing the ring gear its about 2" off to one side of it. I can't imagine it would be able to sling oil hard enough to force it up 3' of tube either. The issue only seems to happen at freewayish speed.

 

[Jbh97009]

I for one have never seen a breather on a diff cover, and I've seen lots of rigs with trusses (including 3 of my own)

My guess, especially since you say it happens at freeway speeds, is that gear oil is indeed being forced out the tube you added. The 'drain relief' you mention is for 35 spline shafts and locker (which I don't think Yukon makes, in a zip anyway) so I don't think that's your issue. I imagine the breather is located out towards the end of the axle tube for this very reason.

I'd either tap a hole in a better spot in the housing or better yet tap a new hole in the tube since you covered your old one. If your truss doesn't have any holes for access, make one. I'd be willing to bet that's your problem...

 

[jeep.kevin]

The 'drain relief' you mention is for 35 spline shafts and locker (which I don't think Yukon makes, in a zip anyway)

You are right. They don't make one, I also never mentioned having 35 spline shafts... :laugh2:

I think I might try putting a baffle in front of the vent hose fitting inside the diff. I think at higher speeds the diff oil is being slung everywhere inside the diff and with the heat and pressure as soon as some splashes on the fitting it gets forced up the tube and out. I can't run the vent to the tubes anymore, all of it is covered with truss or spring perches. Many rigs I've seen with trusses run the vents from the center section or on the diff covers.

 

[Hypoid]

I think I might try putting a baffle in front of the vent hose fitting inside the diff.

I have seen a D-44 cover set up this way, it was on a stock, early '90s Rodeo.

 

[yossarian19]

How hot is the diff getting? If the bearings were set up to tight and the gear oil is getting stupidly hot, I could see it expanding out through.

 

[yossarian19]

How hot is the diff getting? If the bearings were set up to tight and the gear oil is getting stupidly hot, I could see it expanding out through.

Erm... never say never but the best quick-and-dirty math I could do doesn't show this as a strong likelihood.