Tranny oil low, transfer case oil high

[sp543]

I went to check the trans oil level (w56) on my 85 4runner and it was low, probably about an inch, possibly lower below the fill hole. I checked the transfer case level and it was high, so I'm thinking the rear transmission seal is leaking. My question is how dangerous for my drivetrain is it if I leave it for now and just full up the transmission again? Will anything catastrophic happen if the transfer cases are a little over filled? I installed dual cases a few months ago and should have replaced the seal while I had access to it, but neglected to do so.
Thanks