Diff Contamination/Axle Seal Fail/Diff Breather (1 Viewer)

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So I did my big 15k LOF job yesterday. Transmission drain/fill, Transfer drain/fill, engine oil/filter drain/fill, and, crucially, differential drain/fill.

I already have strong suspicions here, but here’s what came out of my front diff. Looks like Birfield soup to me. Annoyingly, I did the Big Axle Job™️ 11k miles ago, so the seals didn’t last very long at all (I didn’t actually HAVE to drain and fill the front diff, but I did anyway, and I’m glad I caught it 4k miles early).

I suspect, among the million other ways the axle seal could fail, that my diff breather was clogged. One, it looks like crap, and was obviously sneezing out greasy BS for a while. Two, I had a significant vacuum pop when I pulled the fill plug, indicating that the diff was generating a good vacuum pull that could have sucked moly past the seals. I have no drips from my Birfs, so for now, it looks like the leak has been one-way.

Although the axle seals will have to be dealt with, my short term band-aid was to replace and extend the diff breather line, if for no other reason than to help with the vacuum issue.

Just adding to the 80 Series Tech forum so others can see the issue in case they get the same thing, and of course I welcome y’all weighing in.

edit: grr, can’t attach the video of the Birfield soup concoction draining from the diff. I’ll try another way in a minute
22BBD24F-ED5D-4FF3-92BB-F1A7755D00C4.png
 
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It's possible that with that amount of vacuum the inner seals on the shafts simply allowed the moly to be pulled into the diff space. If so, then refilling with proper lube and draining several times will help get the moly out. Then refill and drive, AFTER clearing the diff breather port. Recheck after a few hundred miles and see what turns up. If it's just as nasty as before, time to redo the axle service down to the inner seals. If it's just residual contamination, then the seals may be OK. Be sure and check the knuckles and fill with enough moly to mostly submerge the Birf.

If this was your first front axle service, then it may be you damaged the seal or seals when reinstallaing the shafts. If one knuckle seems substantially lower on moly, it could be just that side's inner seal is damaged, which could save you half the work.
 
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It's possible that with that amount of vacuum the inner seals on the shafts simply allowed the moly to be pulled into the diff space. If so, then refilling with proper lube and draining several times will help get the moly out. Then refill and drive, AFTER clearing the diff breather port. Recheck after a few hundred miles and see what turns up. If it's just as nasty as before, time to redo the axle service down to the inner seals. If it's just residual contamination, then the seals may be OK. Be sure and check the knuckles and fill with enough moly to mostly submerge the Birf.

If this was your first front axle service, then it may be you damaged the seal or seals when reinstallaing the shafts. If one knuckle seems substantially lower on moly, it could be just that side's inner seal is damaged, which could save you half the work.
All good points. That was basically my plan as well. Good thinking on one side or the other being the possible issue too, I hadn’t thought of that.

I definitely don’t put it past myself to have damaged the axle seals on install 11k miles ago. Hopefully you’re right that it could have just been the excessive vacuum. Actually, question, I simply took off the old breather hose, deleted the valve at the end, and replaced with longer hose and a little filter (as you can see). I’m wondering if it’s good practice/common to pull the actual fitting off the axle to clean it and make sure it’s not clogged? It didn’t look clogged, but I didn’t take it off and inspect it thoroughly as I was, as usual, in a rush and needed the truck.
 
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All good points. That was basically my plan as well. Good thinking on one side or the other being the possible issue too, I hadn’t thought of that.

I definitely don’t put it past myself to have damaged the axle seals on install 11k miles ago. Hopefully you’re right that it could have just been the excessive vacuum. Actually, question, I simply took off the old breather hose, deleted the valve at the end, and replaced with longer hose and a little filter (as you can see). I’m wondering if it’s good practice/common to pull the actual fitting off the axle to clean it and make sure it’s not clogged? It didn’t look clogged, but I didn’t take it off and inspect it thoroughly as I was, as usual, in a rush and needed the truck.
I know how easy it is to doink one, having done it. Live and learn. I remmbered I was just a little sloppy going in , bumped things just once and what I thought was inconsequential. Nope. So easy you might not remember doing it until it happens to you. You're doing the right thing by keeping watch on the few common failure points in the front axle now/ I won't argue which of the others are most critical, but the hub nuts and the 4 nuts you can see on the bottom of the trunnion box that your steering hooks up to are even more vital safety wise just going down the road. That's the vital 3, with those 2 taken together with that inner seal, that determine axle health and your safety.

As for the breather, if it's higher that whatever was hooked up before then you're better off. If it's higher than whatever water you go through then it'll do it's job (although doesn't ensure against the need to check for water intrusion depending on the case.)

The difference between the two is that the OEM is designed to favor one way airflow. With just a filter but no check valve, then you get 2-way air flow. If you get moisture in the air drawn in, it may condense inside, etc. May not matter depending on where your Land Cruiser goes, but I suspect Mr. T had his reasons for do3ing it the OEM way. It's nothing that needs instant adjustment. Do your due diligence, it's nothing that's going to cause any immediate issues or maybe any at all. I would favor doing it the OEM way, except with whatever extensions are felt suitable.
 
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I had the same thing when I got my FZJ80. Good thing I caught the empty Diff with just the Moly in there before driving 1,600 miles. I just assumed that when the pinion seal failed and leaked all the gear oil out, it caused this lower pressure in the axle and it pulled the moly in. Usually you get the gear oil in the knuckles.
 
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I had the same thing when I got my FZJ80. Good thing I caught the empty Diff with just the Moly in there before driving 1,600 miles. I just assumed that when the pinion seal failed and leaked all the gear oil out, it caused this lower pressure in the axle and it pulled the moly in. Usually you get the gear oil in the knuckles.
The fact that the diff oil picked up moly, but the trunnion box did not seem soupy, was one reason I mentioned trying to see if only one inner seal failed or possibly just the vacuum pressure caused the leakage. A seal failure typically passes both ways after awhile. I ran ours that way for a couple of years while working on my dissertation and simply didn't have the time or money to address the problem. So long as there's plenty of "liquid" in the trunnion box, the Birf likely won't fail. Longer term issues with the diff could arise because of the moly, however, but there always seemed enough lube so long as I checked and topped both of them off.
 
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The fact that the diff oil picked up moly, but the trunnion box did not seem soupy, was one reason I mentioned trying to see if only one inner seal failed or possibly just the vacuum pressure caused the leakage. A seal failure typically passes both ways after awhile. I ran ours that way for a couple of years while working on my dissertation and simply didn't have the time or money to address the problem. So long as there's plenty of "liquid" in the trunnion box, the Birf likely won't fail. Longer term issues with the diff could arise because of the moly, however, but there always seemed enough lube so long as I checked and topped both of them off.
I went out to inject some moly into these suckers and, lo and behold, looks like one side clearly failed and the other was spared. Passenger side looks shiny and lubricated, and had plenty of grease in the housing. Driver side shows corrosion, and took two tubes of moly grease to fill. Your one side failure hypothesis seems to fit.🍻

Now to see if those two tubes of moly grease I painstakingly hand pumped in there disappear into my diff again😂

0E58709B-0CA2-4250-A380-33255BE88CFE.jpeg


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SNLC

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We get Cruisers in the shop all the time with plugged axle breathers. We had one the other day when we took the hose off the axle sucked air for 3 seconds! 😳

They clog, clogged breathers blows seals. People should check and clean them more often. It’s part of a knuckle or rear hub job in my shop. We also check them during 150-point inspections.

Cheers
 
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I went out to inject some moly into these suckers and, lo and behold, looks like one side clearly failed and the other was spared. Passenger side looks shiny and lubricated, and had plenty of grease in the housing. Driver side shows corrosion, and took two tubes of moly grease to fill. Your one side failure hypothesis seems to fit.🍻

Now to see if those two tubes of moly grease I painstakingly hand pumped in there disappear into my diff again😂

Ha, more likely they will keep puking out around the wiper seal there at the knuckle. So long as you keep the diff filled, it minimizes, but won't eliminate, crosscontamination.

SNLC has a good point about checking those breathers. I could stand to do mine right now. Even if the damage is on one side, still check those breathers. Maybe it just blew out the weak or damaged side, so could still be part of the story here.
 
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I went out to inject some moly into these suckers and, lo and behold, looks like one side clearly failed and the other was spared. Passenger side looks shiny and lubricated, and had plenty of grease in the housing. Driver side shows corrosion, and took two tubes of moly grease to fill. Your one side failure hypothesis seems to fit.🍻

Now to see if those two tubes of moly grease I painstakingly hand pumped in there disappear into my diff again😂

View attachment 2640548

View attachment 2640549
Temp solution, right? You'll rebuild the knuckles and change the seals soon I hope.
 

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