Transmission/xFer Case Fluid Cross-flow

[cruiser_guy]

Who is your supplier cruiser guy ?


Robert. Yes as an insurance. I think I got away with it lightly this time, but I would not like to chance it again.

Bennet I think it's just flows from one case to the other when the levell rises in one rises above the other.

Mick

I think the name was "National Hydraulic" or something like that in Surrey, B.C. If you do a search you should find a parts list from the stuff I bought about 6 months or a year ago, I think the supplier name is there too.

I brought in the filler plug and they gave me two 90 deg. elbows that fit the same metric thread as the filler plugs (no tapping or drilling the plugs) and could be oriented which ever way I wanted AFTER they were tightened down, as well as two barbed fittings for the elbows to attach the hose to. Got some oil resistant hose at Lordco and all was fine.

I've since replaced the seal when I did my clutch this summer and the crossover pipe is in my toolbox for the next time the seal goes. I think the transfer case vent plays a large part in the failure of that seal as well so I rerouted the transfer case vent up to the top of the firewall along with the rear end vent. I've still got to do the front diff vent yet.

 

[Mick]

I've since replaced the seal when I did my clutch this summer and the crossover pipe is in my toolbox for the next time the seal goes. I think the transfer case vent plays a large part in the failure of that seal as well so I rerouted the transfer case vent up to the top of the firewall along with the rear end vent. I've still got to do the front diff vent yet.

Thanks, I just sent them an email asking for the elbows, I hope they can remember which threads are the right ones for the job.

What makes you think that the vent may be responsible for the seal failure ?


Micck

 

[burnt03]

C_guy, from your old post I gather the part numbers are as follows....

elbows: 10-1JH9-08-18-OG
fittings: 10-26712-08-08

Not entirely sure if those are correct or not, they were sort of mixed up w/ old quote commands in the post. Mick, if you figure out the correct thread size/pitch, could you let me know?

Thanks!

 

[lone gunman]

definetly check around the local hyd shop only charged me about $25.00 for the fittings and 2 ft of hose. but that was 2 years ago. i dont remember thread size. i will look around and see if i can find the box, i know i kept it because the ald plugs are in it.

 

[lone gunman]

ok found the box, its made by parker hannifin corp, tube fitting division 3885 gateway blvd columbus, ohio 43228. part #8M18C80MXS so i believe they are 18mm threads like i said i got them localy but i believe they do have a web site. good luck!

 

[cruiser_guy]

My theory is that as you run the truck naturally the tranny and transfer get warm thereby increasing pressure inside the transfer, if the vent works properly that excess pressure is vented, if not the oil is forced through the seal. It doesn't flow back to the transfer when cold because the tranny vents easily through the shifter.

 

[Mick]

If you go fill-to-fill, yes, it will go both ways (insert David Bowie joke here)

The problem I have experienced is that the transmission oil is ending up in the transfer box, not the other way around.

If I were to rely on the tube system would the transmission run dry due to the different levels between the filler access points, before the transfer box got to a sufficently high level to transfer the gear oil?


Mick

 

[OswaldtheBold]

On my '68 FJ40 (3 speed, old transfer) the oil moves from transmission to transfer. No, the MAF fill-to-fill hose will not solve this problem (although I think Landpimp once posted a photo of a clever pump setup he found on an old transfer that moves the oil back to the transmission fill.)
My '85 FJ60 (4 speed, split transfer) the oil goes from transfer to transmission, and the fill-to-fill hose permits the excess to return to the transfer. But, because the transmission fill is angled upwards at an angle and the elbow fitting is about an inch long, the transmission oil must be overfilled about an inch before it will start to return through the hose. I fill both cases, run it around a bit to move the oil, then top up the transfer, and this seems to work.
And No, it won't go both ways. The difference in height between the fill plugs is too great, unless you are seriously pressurizing the transfer.

 

[Mick]

Thanks Oswald, you confirmed my suspicion.


Mick

 

[tobydog]

One other plus to the hose. Use clear hose and if you don't over fill you should not see oil in the hose. If you do you know your tcase is overfilling. Win win for both problems.

 

[JohnL]

Thanks guys. I checked my levels again this weekend and I'm getting flow from the t-case to the transmission. I have about 1000 miles since the last fluid change and the transmission was 1/2 inch high, the t-case 1/2 inch low.

Gear oil stinks.

 

[PabloCruise]

On my '68 FJ40 (3 speed, old transfer) the oil moves from transmission to transfer. No, the MAF fill-to-fill hose will not solve this problem (although I think Landpimp once posted a photo of a clever pump setup he found on an old transfer that moves the oil back to the transmission fill.)
My '85 FJ60 (4 speed, split transfer) the oil goes from transfer to transmission, and the fill-to-fill hose permits the excess to return to the transfer. But, because the transmission fill is angled upwards at an angle and the elbow fitting is about an inch long, the transmission oil must be overfilled about an inch before it will start to return through the hose. I fill both cases, run it around a bit to move the oil, then top up the transfer, and this seems to work.
And No, it won't go both ways. The difference in height between the fill plugs is too great, unless you are seriously pressurizing the transfer.

Bingo Oswald! The difference between the fill hole levels is real.

Do a search on the LCML. Mark Whatley wrote that when the seal is first failing, you will pump fluid from t-case to the tranny. Then, when the seal lets go, fluid will flow from tranny to t-case. Sounds like the best thing to me is to save your money, don't buy fittings and hoses, rather buy a new seal...

 

[Cruiserless]

During my search for threads on fluid passing from the transfer case to the transmission I found this ancient thread... any updated opinions on the "fill to fill" hose idea? My transmission fluid level was high and xfer case level was low.

Also, the fluid from the transmission was a thick brown clumpy mess. Is this normal? No metal shavings that I could detect. I trailered it home after purchase so the history is unknown other than it had not been driven in a few years.

Russ

 

[Fast Eddy]

Not normal at all. It probably got water in it? You might want to pull it all apart, inspect it and replace the seals.

There are other threads on this hose if you insist. Check the FAQ.

 

[SteveH]

Remove the OEM vent cap on your xfer case, and this prevents the xfer case pressure from pushing the oil into the transmission. I have done this on a '78 40 and an '87 '60, and it fixed both. There is no reason for the oil to 'want' to swap cases, unless you have pressure in the cases. Doing this will also lessen the leaks from the parking brake seal on an '40.