I changed the oil in the transmission and transfer case today in my 82 FJ 60. I drained more out of the transmission and less out of my transfer case . (About 1 1/4 gallon out of the transmission and only about 1/4 gallon from the transfer case.) I read somewhere on this site about a possible vent problem on the transfer case causing this but I can not find the post. I felt around on top of the transfer case and found the vent . I wipe it off with a rag . It seems to "jiggle" side to side and up and down like a relief valve on a pressure cooker. Any help will be greatly appreciated.
Need help with transfer case vent !
- Thread starter pdugas
- Start date
Content may include affiliate links. Please see terms for details.
There is an oil seal between the transmission and transfer case. If this is leaking the oil can move from the transfer case up into the transmission. There is a bypass hose that will connect the two fill ports allowing the over full transmission to drain back down into the transfer case.
When I removed my transmission and transfer case, I replaced that check valve with an elbow/adapter (pipe thread to hose barb) and connected a hose that runs up into my engine bay. I also extended the differential breather lines up. But I'm not sure you can do that conversion with the transmission and transfer installed on the truck. The OEM vent is press fit into a smooth hole and to install the elbow/adapter you need to use a tap thread that smooth hole.
The bypass hose works as long as the leak is from transfer to transmission. The real fix is to replace the seal, which minimally requires disassembling the transfer case. If you go this route, investigate whether the same seal for the FJ62 will fit. this seal is a double lip seal and should last longer.
When I removed my transmission and transfer case, I replaced that check valve with an elbow/adapter (pipe thread to hose barb) and connected a hose that runs up into my engine bay. I also extended the differential breather lines up. But I'm not sure you can do that conversion with the transmission and transfer installed on the truck. The OEM vent is press fit into a smooth hole and to install the elbow/adapter you need to use a tap thread that smooth hole.
The bypass hose works as long as the leak is from transfer to transmission. The real fix is to replace the seal, which minimally requires disassembling the transfer case. If you go this route, investigate whether the same seal for the FJ62 will fit. this seal is a double lip seal and should last longer.
- Thread starter
- #3
Oil migration from transmission to transfer or the other direction happens to all high mileage 4WD vehicles that have a transfer case - not just the 60 series. It’s just the nature of the beasts (worn oil seal).
You can rebuild the transfer case and replace the input shaft oil seal that’s leaking — but it’s going to leak again eventually anyway. Replacement will just give you a short reprieve.
Another way to deal with it is just check the oil levels in the transmission and transfer case every few weeks or months until you get a feel for how fast it’s migrating. Then adjust as needed.
That’s what I did for 25 years. Kind of a pain but it became 2nd nature to check the oil levels occasionally. Never ran into problems using this method.
The only time I DID run into problems was when I finally gave up and installed that damn bypass hose that drains excess oil from the transmission to the transfer. That cursed hose gives the user a false sense of security when it’s very possible that the oil might migrate THE OTHER WAY, with the transmission filling the transfer - which then makes the hose useless.
But once the bypass hose is installed, the user thinks he can get away with not checking oil levels anymore (which he can’t) so he runs the transmission low on oil for thousands and thousands and thousands of miles - thinking (wrongly) that everything is fine — when everything definitely isn’t.
So if you’ve got to check the oil levels anyway, regardless if you’ve got that blasted bypass hose installed, why use it at all? It’s more of a pain removing it each time to check levels than just unscrewing a fill plug.
You can rebuild the transfer case and replace the input shaft oil seal that’s leaking — but it’s going to leak again eventually anyway. Replacement will just give you a short reprieve.
Another way to deal with it is just check the oil levels in the transmission and transfer case every few weeks or months until you get a feel for how fast it’s migrating. Then adjust as needed.
That’s what I did for 25 years. Kind of a pain but it became 2nd nature to check the oil levels occasionally. Never ran into problems using this method.
The only time I DID run into problems was when I finally gave up and installed that damn bypass hose that drains excess oil from the transmission to the transfer. That cursed hose gives the user a false sense of security when it’s very possible that the oil might migrate THE OTHER WAY, with the transmission filling the transfer - which then makes the hose useless.
But once the bypass hose is installed, the user thinks he can get away with not checking oil levels anymore (which he can’t) so he runs the transmission low on oil for thousands and thousands and thousands of miles - thinking (wrongly) that everything is fine — when everything definitely isn’t.
So if you’ve got to check the oil levels anyway, regardless if you’ve got that blasted bypass hose installed, why use it at all? It’s more of a pain removing it each time to check levels than just unscrewing a fill plug.
Yeah it’s my opinion that those bypass hoses suck.
For one, the hose fitting that screws into the transmission fill hole is about 1 inch higher at the pipe bend than the recommended full level on the transmission. That means that the transmission will always be overfilled — by a lot, if oil starts migrating upwards.
Overfilled transmission messes with shifting- it gets notchier- and the oil finds a way out the input shaft seal into the clutch inspection cover - making a mess there.
I had one of those bypass hoses for a few months (ran my transmission low on oil because of it) and soon discovered that dealing with it created a mess when having to manually adjust a level.
I gave it a try - and I hated the thing. Tossed it in a dumpster. They give a false sense of security which can lead to destroying the transmission if you just set and forget.
4runner2FJ60
SILVER Star
Not the hose I have, its braided ss. I also fell victim to the bi-pass hose "fix" It will be removed soon when I do the rebuild. Every time I check it something needs correcting. Before hose, all oil was up in transmission. After hose, now its all in xcase.
Split the case and pull the gears so you have access to the input seal. Replace the seal with a new one but use a FJ62 seal which has double lips, and check the breather vent.
@shipmag
Sells these - not sure if still does. Very heavy duty and will last until you tear the T'case apart. Obviously, the threads on t'case and trans have to be good.
forum.ih8mud.com
Sells these - not sure if still does. Very heavy duty and will last until you tear the T'case apart. Obviously, the threads on t'case and trans have to be good.
Transmission to Transfer Case Bypass Hose
Go to last thread for current pricing. The first 5 group buys were done at this url Tranny to Transfer case bypass hose if you want to know the history or look up how others have done with this product click on the link. I am now ready to open group buy 6. As I am only ordering 5 at a time my...
forum.ih8mud.com
Thanks for the Mention Spike Strip. Yes i still carry these. Have sold over 500 of these hoses. I have both sizes in stock. All monies go to help pay for my mission work to provide jobs for the poor in the tropics. We convert banana stems into fabric. If any one knows about growing pectic enzymes contact me as we are dead in the water on the project.
The earlier transmissions are more prone to leaking as they have a single lip seal on the output shaft between the transmission and transfer and no o-ring on the transfer input gear. Later boxes have shorter splines on the output shaft which allows an o-ring to seal the nose of the transfer input gear against the shaft and the output shaft rear bearing. They also have a double-lipped oil seal between the two.
The more modern transmission/transfer combinations have an oil-free extension housing between the two where oil could disappear were the seal to fail, yet it's not a common problem, so I don't buy the idea that the things are destined to leak. Still very good practice to keep a regular check on fluid levels.
The more modern transmission/transfer combinations have an oil-free extension housing between the two where oil could disappear were the seal to fail, yet it's not a common problem, so I don't buy the idea that the things are destined to leak. Still very good practice to keep a regular check on fluid levels.
Last edited:
