After reading a lot of helpful stuff on the forum, and taking care of a few things (rear upper control arms for reduced tire wear...), I decided to heed the general advice about servicing the transfer case fluid.

My car is an '03 2.5L automatic. My transmission seemed to hesitate at times when shifting (not always, but sometimes after decelerating to a slow speed and then getting back on the gas again). Was also leaking a little bit of something that didn't look like the normal oil leak (oil pan gasket FTW!)...

So I got under to remove the drain plug on the transfer case (easy enough to do, although not everyone makes it clear that it's a strange bolt requiring the actual stub of a 1/2 inch drive, with no socket on it!), and based on what has been written here I was expecting either nothing to come out, or a bit of gooey gear oil...

Instead I got a big rush of very liquid black fluid! About 500ml worth. It looked a lot like used ATF, although it didn't stink quite as bad as ATF normally does. But what else could it have been?

So, after reading up on the common cause for ATF leaking into the transfer case, it looks like the damaged seals can't be replaced without rebuilding the unit (or buying a freshly rebuilt one). And since I don't know how much damage might have been done already, I'm not sure rebuilding it would be worth the hassle if I can just but a better rebuild.

Either way, my plan for the meantime is just to drive the car as is. I can't stand leaks, but I've already learned to reluctantly live with the oil pan gasket leak for now, so what's one more?

Also, I've read in several places that ATF can actually be used in a transfer case instead of gear oil. It's not better, but it can be done.

So what do you all think? Am I crazy? How long do you think this freakish arrangement might last?

 

Not long!

I would say put 300 mls of 75W 140 gear oil in the transfer box (to go with the 250mls already there, left when you drained via the standard drain point) Run with that for enough miles to mix it all up, then continue draining and filling with 300 mls until you're happy its virtually all 75W 140 coming out instead of whatever was in there before.

If there is then leakage from the transmission, the excess fluid mix will blow out through the vent on top of the transfer box and run down the right hand side of the box to indicate trouble.

Then check/top up or replace the transmission fluid, referring to this link

https://www.jaguarforums.com/forum/x...ure-faq-43649/

 

That is essentially what I am doing. When I drained the liquidy mix out last week, I refilled with 75W-140 Gear oil only (took roughly 250ml - 300ml as expected). And I do plan to do it another time, to at least get some clean gear oil in there.


Thing is, I'm almost 99% sure that the ATF to Transfer Case leak already exists, and that it was already blowing out the top vent (it was a total mess under the car. So covered with fluids it was hard to determine the exact origin. But that's my hypothesis).

So even if I get clean, fresh gear oil into it, eventually the ATF will creep back in and start mixing around. I'm just thinking it might not be the worst thing in the world. First because the gear oil is heavier, and should settle to the bottom under the ATF, and second because running ATF in a transfer case is apparently recommended for some cars (not the X-type, mind you, but it isn't totally unheard of). If I will have to replace the case eventually, might as well go like this for as long as possible. No?

 

It sounds as though you have a definite leak into the transfer case. The problem is, that as the excess fluid in the transfer case vents and flows out, you are continually lowering the amount of fluid in the transmission.
You are toying with a complete transmission failure if that leak isn't fixed.
Adding gear oil to the transfer case is not going to stop the ATF from getting into the transfer case.

 

What I was suggesting was so that you can establish a known base/starting point to work out how bad/fast the leak between the two boxes is. But it will be more of an art than a science. As Avern1 says, it's the main box that you need to watch to avoid major expense.

Fitting a used transfer box would probably be the easiest, quickest and most economic solution. But try to ensure the link shaft has never been removed without removing the circlip on its inner end as that's what does for the inter box seal.

 

Thanks for the replies, guys.

Agreed. I'm under no illusions that the gear oil will somehow stop the ATF from getting into the transfer case, and I do indeed intend to keep a very close eye on the ATF level in the transmission.

This shouldn't be too bad, since the transmission is very easy to drain and refill.

Last week, when I went through this stuff for the first time, I was actually surprised at how much ATF came out when I drained it. Around 2.5 - 3 quarts, which I believe is about right for simple drain procedure through the plug. It it makes sense, because the Transfer case had about 600ml of liquidy crap come out of it, and the leak is really just a few drops here and there.


Astromorg, I will be trying to monitor how quickly the leakage takes place. And I read about this famous circlip damaging the seal, which makes me leery of any used unit.

 

If your passenger side axle with the intermediate shaft was not removed it is hard to imagine that two seals in series, that separate the two oils would both go bad, unless the axle shaft bearings have had it ( due to lack of lubrication at some point) and it wobbles. Rebuilding the transfer case is fairly simple and straight forward. It will cost you less than couple of hundred dollars if you do the work yourself. I would not buy a transfer case from junkyard as it may be no better than the one on your car.