H55F Oil, passage from the T-Case to the gearbox or the opposite. (1 Viewer)

[Guillermo Dubosc]

H55f T-case Oil passage from the T-Case to the gearbox or the opposite.

To think about, I recently upgraded my H55F and the tcase. I found the oil seal that separates the gearbox and the T-case detached from the outside.
Why is this happening?
which leads me to think of a bad placement (which I did 3 years ago) or another factor.
What I discovered, my interpretation of the problem is as follows.
The T-case vent is a one-way valve that only removes the gas or pressure to the outside, preventing overpressure inside the T-Case, but in the gearbox the vent is done by the rubber on the lever change which allows gas to enter and exit, maintaining the pressure equal to atmospheric pressure inside the gearbox.
Returning to the T-case, when the T-case heats up due to use, the oil and gas inside expand and vent to the atmosphere, but when it cools it cannot re-enter, therefore a vacuum is generated inside the T-case. -case this causes all the oil seals of the T-case to be sucked into the case but the only one that does not have a backrest, meaning it cannot move inside the T-case, is the one that separates from the case, so I found my oil seal moved to the T-case.
In this way, I eliminated the non-return valve from the T-case vent and put a hose that vents to the atmosphere where the gas can go and return without generating a vacuum or pressure, the pressure inside the T-case being equal to that of the gearbox and equal to that of the atmosphere The end of the hose is in a hi place of the truck..

 

[coldtaco]

Not having taken a thorough look at the transfer case, I would assume that the vent is a two way vent. It's supposed to "close" when under water and stay open the rest of the time. I would say your vent was dirty and stuck?

 

[Guillermo Dubosc]

good day
This valve is only one way, it is a valve that only vents outwards.

 

[Eurasiaoverland]

good day
This valve is only one way, it is a valve that only vents outwards.

View attachment 3482286

Incorrect. If working correctly, you should be able to push the cap of the valve down to seal it. The spring rate is very small, so that the additional density of water when submerged will close it.

If you tested your valve and found it to only seal one way, it is defetective.

Leaks between transmission and transfer are common on the H55F, particularly earlier (I think pre 1987) versions which had single lip seals and no o ring on the transmission input gear.

If the seal had come out completely, I would assume either use of an incorrect or substandard quality component, or incorrect installation.

even if thevalve was blocked, it would take a lot more pressure than thermal expansion of the air in either block to physically blow the seal out, if that is what you meant.

 

[Guillermo Dubosc]

Good day how are you my friends
Without interest in arguing, it is possible that my conclusion is wrong. BUT. BUT as they told, this problem is common and it seems to happen without a clear explanation. Therefore, it made me think about another angle.
The Tcase vent valve is a valve designed so that at least no water or mud enters from the outside, but mine was apparently in perfect condition and did not let air in either (could it be just in my valve?) or in many the same thing happens.
I have installed hundreds of oil seals and close to 0 have failed. In this particular case, I paid special attention knowing the problem (just to think about).
Also this oil seal when it is a single lip seal the spring goes to the side of the Tcase (contrary to what one would think trying to cut off the oil from the gearbox, I think this is because the designer thought about allowing it to pass gas through the seal when the Tcase cools and the vacuum created is filled from the gearbox that is connected to the atmosphere.
Let's think about the following situation: a vehicle comes hot and gets stuck in a deep well with water and mud. The water level exceeds the vent valve. The box is submerged in water and cools quickly. Where does the air enter the Tcase since when it cools a vacuum is generated inside it? Just to think.
In my interpretation, the seal between the gearbox and the Tcase allows in this situation to let a small amount of air pass through to equalize the pressure between the two boxes.
Just to think together?G

 

[Eurasiaoverland]

Good day how are you my friends
Without interest in arguing, it is possible that my conclusion is wrong. BUT. BUT as they told, this problem is common and it seems to happen without a clear explanation. Therefore, it made me think about another angle.
The Tcase vent valve is a valve designed so that at least no water or mud enters from the outside, but mine was apparently in perfect condition and did not let air in either (could it be just in my valve?) or in many the same thing happens.
I have installed hundreds of oil seals and close to 0 have failed. In this particular case, I paid special attention knowing the problem (just to think about).
Also this oil seal when it is a single lip seal the spring goes to the side of the Tcase (contrary to what one would think trying to cut off the oil from the gearbox, I think this is because the designer thought about allowing it to pass gas through the seal when the Tcase cools and the vacuum created is filled from the gearbox that is connected to the atmosphere.
Let's think about the following situation: a vehicle comes hot and gets stuck in a deep well with water and mud. The water level exceeds the vent valve. The box is submerged in water and cools quickly. Where does the air enter the Tcase since when it cools a vacuum is generated inside it? Just to think.
In my interpretation, the seal between the gearbox and the Tcase allows in this situation to let a small amount of air pass through to equalize the pressure between the two boxes.
Just to think together?G

View attachment 3482971

Hi G,

Apologies; you are correct. I checked a new valve and indeed, it is a one-way valve at all times, the spring/cap must be just to keep out dirt. This may indeed be (part of) the reason for the oil transfer. I still think the pressure difference would not be great enough to blow out the entire seal, having hammered one in myself. I have a W59 gearbox which has a factory pressure transfer hose between transmission and transfer; maybe that is the key modification to stop oil transfer.

EO

 

[Guillermo Dubosc]

EO
Good day.
I maid a vent hose link by myself betwin the transfer a gearbox to mantain the same presure in both boxes.
By G