Theory - Extra oil in transmission and low in transfer case

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CarcaineProblems

CarcaineProblems

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This is a much discussed topic here - if the oil level is low in the transfer case, but high in the transmission, the likely culprit is the seal between the two is bad.

What I haven't heard is why that seal goes bad, so I wanted to get the groups opinion on my theory. Keep in mind that I'm no where near as mechanically inclined as most here are - I wouldn't be able to drop the transfer case, split it open and rebuild it. So I wouldn't be surprised if my theory is blown out by some basic mechanic 101 info that I don't know of.. :doh:

In my truck I have the h55f and the standard split case. There isn't a breather on the transmission, but apparently it breathes through the big hole at the top where the shifter is. There is a breather on top of the transfer case, but its that crappy factory style breather that is butted up against the floorpan:

transfer-case-1a-jpg.414213


So knowing these two points, does it make sense that oil is 'pumped up' into the transmission and the seal fails because the breather on the transfer case is clogged/stuck/broken? Therefore the only place for air is through the top of the transmission? In the process of pushing air it moves fluid too??

I'm basing a lot of my understanding on post #3 and #4 in this thread: https://forum.ih8mud.com/threads/transfer-case-leak-maybe-tranny.522613/

I'm having this very problem - i open up the fill on my tranny and it comes pouring out. I open up the fill on my transfer case and its low.

I ordered the equalization tube from Spector (spendy and $75!), but I'm trying to understand the root cause. AFAIK, the transfer case was rebuilt 4 yrs ago when the h55f was put in (prior to my ownership).


Don't mean to beat a dead horse, :deadhorse: just trying to understand it a bit better.

Thanks
 
I had the reverse issue going on in 20k miles or less. I was told the added hose would not help when fluid moves INTO the TC. Was also told that the newer updated 62 seal is better than a 60 seal. Al at MAF recommended lots of grease on the inner valley of the seal, and that not having grease there causes added friction and heat and early failure of the seal. Makes sense to me.

When I had mine redone the second time I mentioned the extra lube theory to the tranny shop and the guy looked surprised that I would suggest it. He said oil will get slinged up there and get lubed just fine. I replied that it went out in less than 20k miles so it can't hurt to give it some lube.

So, adding to the theory, maybe most tranny shops don't add grease inside the seal causing the seal failure. I wasn't there when the pieces and parts went back together so I can only hope this time things stand up longer than a few years.
 
Sounds like a sound theory to me. As the temperature inside the cases (whether transfer, transmission, or differential) rises, gases expand.
The vent is there to allow the expanding gases to escape, but prevent water from getting into the case.
If the vent is clogged, pressure inside the case builds as the temperature rise (under operation) and the path of least resistance for the gases to escape now becomes that seal.
As the gases push their way out, they also push any fluids that might be in their way. Rude gases.

So, if you clean that vent, so the path of least resistance becomes the vent again, as originally designed, then you should see the symptoms you are describing stop.

Folks often remove that vent and tap in a brass hose fitting, and then run a hose high up into the engine compartment.

How would you remove the vent and tap a hose fitting with the transmission/transfer case on the vehicle?

Or is there a way to clean the existing vent?
 
Thx @jfnall - i will keep this in mind as i get closer to a rebuild...

Slow Left said:
How would you remove the vent and tap a hose fitting with the transmission/transfer case on the vehicle?

Or is there a way to clean the existing vent?
Click to expand...

The only way I come up with is to cut a hole in the floorpan to gain access to the breather. Then tap it, put a barb fitting on it and connect a breather line:

P1010019-3.jpg


Maybe use a 90 degree fitting??
 
CarcaineProblems said:
Thx @jfnall - i will keep this in mind as i get closer to a rebuild...



The only way I come up with is to cut a hole in the floorpan to gain access to the breather. Then tap it, put a barb fitting on it and connect a breather line:

Maybe use a 90 degree fitting??
Click to expand...

Aggressive. I like it.

Did you already cut the floorpan and do the tap, or is this just an idea that someone else went through and you're keeping it on the table?

Other thing to consider is, when doing the tap, how do you keep the metal shavings from falling into the inside of the transfer case? Or, if shaving accidentally fall into the inside of the transfer case, what risk does this pose to the gears/seals, or would that risk be manageable by just doing a gear oil change right after you do the fix and right before you drive it for the fist time after the fix.
 
Just thought of something. Maybe the 'filler' hole is close enough so that you could insert something in the 'filler' hole to catch any falling shavings. Like say a net made of panty hose stretched over a frame made of a wire coat hanger or something crazy like that.
 
On the other hand, if you wanted to try and take the approach of cleaning the apparently clogged OEM vent, then you could repeatedly (...I'm thinking 2x a day...for ?? days) spray a solvent like Seafoam up under the cap of the vent and let it do it's thing and hopefully break up any hydrocarbon clog. I say Seafoam, because it is really good at stuff like that. I use it to clean the PCV valve...just let it soak in Seafoam overnight, then blow dry with pressurized air.
I think I remember hearing both sides of the argument that the vent cap can/cannot be removed and then replaced. I would try it without removing it.
 
@Slow Left -great suggestions. I think @Lugal might be on to something regarding the venting....

If taping the fill plug creates anothe vent, wouldn't the "equalization tube" that ties the tranny and transfer case fill plugs together create another venting route for the transfer case (up through the transmission)??

I should have the equalization setup from SOR by Thursday or Friday. Stay tuned for results....
 
Lugal said:
Yeah, I wasn't thinking clearly. Tapping the plug would definitely not be compatible with the equalization tube.
Click to expand...

BUT, the idea is sound - find another way to vent the transfer case w/o getting fillings into the oil. Linking the 2 fill plugs together should fix this, correct???
 
Yeah, try the simplest solutions first and see if the fluid levels stabilize.

Do a MUD search on ATF mixing with transfer gear oil (this is an FJ62, right?) and see if there are problems/solutions dealing with this.
 
With respect to the risk of shavings falling into the transfer fluid, I'm wondering if that isn't a smaller risk than I originally thought.

If the transfercase housing is made of aluminum (I think it is - which is not magnetic so can't use magnets to guide the shavings where you want them...), then maybe a gear oil change right after you do the fix might be sufficient.

The gears and bearings inside the transfercase are large and would probably make short work of any small shaving remnants. It's not like having iron shavings in the engine oil that could wreak havoc on bearings/rings.

I don't know, it's gotta be a judgment call on your part if it goes that far. How desperate are you to avoid pulling the transfercase apart vs the risk of being forced to pull the transfercase apart if a bearing goes as a result of the shavings...
 
I cured the 'overfull transmission and underfull transfer case' problem on my '87 FJ60, '78 FJ40, and '76 FJ55 by putting a vent hose on the xfer case nipple. Pry off the steel cap and install a section of 3/8" fuel line on the remaining nipple, and clamp it on with a hose clamp.

I strongly recommend it. If the vent is plugged, it will do this even with a decent seal. It's tough to get access to the breather on any truck, but lowering the xfer case would help.
 
Slow Left said:
Aggressive. I like it.

Did you already cut the floorpan and do the tap, or is this just an idea that someone else went through and you're keeping it on the table?

Other thing to consider is, when doing the tap, how do you keep the metal shavings from falling into the inside of the transfer case? Or, if shaving accidentally fall into the inside of the transfer case, what risk does this pose to the gears/seals, or would that risk be manageable by just doing a gear oil change right after you do the fix and right before you drive it for the fist time after the fix.
Click to expand...


hahaha, sorry, love the comment on aggressive, seriously, nicely done
 
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