I checked my t-case level this weekend and was surprised to find it was overfull. The oil appeared dark greenish and had tiny bits of black throughout it (must be part of the seal). After the oil drained on my driveway I checked the tranny and still seems to be full, actually that seems slightly overfull too but not sure how?? 

Anyways, I'm gonna assume the seal seperating the trans and tcase is damaged, and I'm wondering how big of a job it will be to change.   Specifically, I'm wondering if anyone can tell me if I need to pull the whoie trans or if I can just pull the tcase?

Also, what do folks think about the lucas atf additive?  I have a bottle to try so if it doesn't work no problem but, I don't want it to damage my trans. 255000km on the truck (01 vitara) and I was thinking of getting a new(er) one next year so maybe I can make it last another year by just draining the tcase and topping the atf once in a while?

Why, if the tranny is full, are you assuming it's leaking into the transfer case?
Why, if the fluid in the transfer case is greenish, are you assuming it's ATF?

Now I can understand if the transfer case is "over filled" and the transmission low, or if the transfer case fluid were reddish and overfilled, why you would think there was cross contamination.

Refill the transfer case and correctly check the transmission level - I believe it needs to be done with the transmission warm, engine idling and transmission in neutral (feel free to correct me if that's wrong) - and monitor the levels for the next few days/weeks, and then worry about it - if necessary.

Oh - the mysteriously overful transmission - I'm more of a manual transmission type, and only one of my vehicles has an automatic transmission - an Aisin Warner AW4 - which I believe is the same one used in the GV - if I check the fluid level with the engine off, it will always show high, and at first I was concerned, but then I discovered that I was checking it incorrectly, and it had to be checked as described above.

Edit.

I checked the owner's manual for my GV - Suzuki lists a similar process to the above, but stipulates that the fluid be checked with the transmission in park, and after manually selecting all of the "gear" positions to ensure all of the fluid circuits are full.

Thanks...maybe i shouldn't be so quick to jump to conclusions.  I guess the fact that there are hundreds of little black bits makes me think the seal is gone.  I was unaware of proper procedure for checking the ATF level.

There is no real direct way for ATF to get into the transfer case, they are isloated from each other.

Oh wow, thanks I was under the wrong impression!  I guess I must have just overfilled it somehow

How did you fill up the t-case last time?