So i have a new to me 4runner with a chevy 4.3 - 700r4 - advance adapters 50-5705 - dual marlin gear driven tcases. I overheated the transmission and blew a few seals, had an atf leak at the bellhousing that went away when it cooled down (could be vent breather). a few days later, i drove about 60km highway and upon arrival i noticed an oil leak coming from the cases, somewhere near the top but im not 100% on that yet. I pulled the fill plug on the rear case, expecting to be low on fluid and found it be overfull by quite a bit. drained it to the appropriate level, checked the trans fluid and it was a bit low so filled it, then drove it back home and found the rear case to be full of fluid again.

my questions are:

-were gear driven tcases like the one i would have in my dual cases offered in a stock toyota automatic transmission?

-does a gear driven tcase like the one i have in my duals have a seal on the input shaft in front of the bearing to stop fluid going between transmission and tcase? depending on the answer to the first question, would it share the fluid between the manual trans and the tcase? if they were available in automatic transmissions, would it rely on a seal on the trans output shaft, the tcase input shaft, or both?

-it looks like there is an oil seal in the adapter itself between the transmission and first case. could this be the only seal that keeps the atf and gear oil from mixing together?