Gearbox and transfer box drain

Hi thanks in advance for any help. Set aside this morning to change oil's on my lt77 gearbox and transfer box. Drained the transfer box fine then when it came to gearbox no oil came out, obviously not good but put the drain plug back on and proceeded to put the oil in then quickly noticed it was draining straight out the transfer box drain! (I know I forgot to put the transfer box plug back on)

Surely there should be a seal between the two as they both take different oil??
Cheers everyone