some have a case oring that is very hard to replace
there are more pages not show, shifter seals, and front end ...
off my 3L30 page
see 16, 21 and 27 , all can leak
also the 4wd transfer class, intersection case (hollow)
as a drain, at the bottom ,if it drips ATF then 14 is bad
if the drain drips, GL4 (not pink, ) the the xfr case seal is bad.