View Full Version : Birf soup

08-05-2010, 02:41 AM
So here is my issue a couple of months back I replaced the birf(used an new OEM birf from Cruiserdan) on the drivers side of my 94 FZJ 80. I also used all new gaskets and Marlin oil seals. Well the other day Treeroot noticed that the knuckle was covered in 90 weight. At the time we assumed that the oil seal had failed. This evening I pulled the knuckle apart only to find the Marlin seal looks brand new and the knuckle was indeed full of 90 weight. I then assumed that maybe the axle itself has a groove, however it is smooth with no visible defects.
The only thing that I have found out of place was that the diff breather was clogged. My question is if that is enough to completely wash the grease out of the knuckle and fill it with 90 weight? Anyone else have this happen or have any idea where I should look?

08-05-2010, 06:26 AM
Wasn't there an issue with this axle being hit as well?

08-05-2010, 09:26 AM
I don't believe so. The only hit the previous owner mentioned was hitting the passenger side bumper on the scoop of a snow plow.

08-05-2010, 09:30 AM
I guess its feasible the pressure built up enough from clogged breather to blow oil back through the seal and into the knuckle.... ??? ...emphasis on 'guess' .....

08-05-2010, 09:56 AM
I've had the pinion seals leak on several 'cruisers with plugged breathers. After unclogging the breather and installing a vent tube, the pinion seal leak stopped. Given that your parts are new, I'd sure unclog, repack, monitor the situation, and not dig deeper for now.

08-05-2010, 10:07 AM
A clogged breather will DEFINITELY cause leakage. Whatever the weakest seal is, that is where you will leak.

The temperature change from a cold axle to a hot one is several hundred degrees. P1/T1=P2/T2, so the pressure inside without a working breather is increased several hundred times when you go from cold to hot.

08-05-2010, 12:53 PM
Agreed with others from what I've read and specifically with regard to the 80 series...

I'm still getting moly grease into the gear oil in my front diff after my rebuild last year. After searching around MUD I found threads/posts from others with the same experience and the answer as to why appears to be a blocked diff vent causing a vacuum. In my case it seems to be more from the knuckle to the axle vs. your situation. Regardless, I'm going to extend the breathers and I'm betting when I do so I'll find that the diff vents are blocked.

08-05-2010, 01:12 PM
I decided to put it all back together and run it. Hopefully it was just the breathers. I am hoping somehow I didn't bend the axle housing.

08-06-2010, 08:53 AM
Ye'all jut need to swap out all your Lube and grease w/ backwoods goop ! Duh.... Rookies...... Lol:lmao:

08-06-2010, 09:24 AM
Ye'all jut need to swap out all your Lube and grease w/ backwoods goop ! Duh.... Rookies...... Lol:lmao:

LOL!!! :thumb::thumb:

08-06-2010, 09:37 AM
I think that's why it's leaking out is because it's goop...

08-06-2010, 11:52 AM
The diff was overfilled so that could have added to the creation of birf soup. I'll have to check where the fill plug is in relation to the axle seals but the 90 weight gets in there on a regular basis. I know mine dropped a lot of 90 weight when the rig was slightly leaning toward one side. We knew the failure there because the wheel fell off. Did you fill the diff and then add the lift? The caster correction rotates it slightly so that may be why you were able to over fill it on level ground.