I've just replaced the transmission in a 96 Tahoe 4x4, 5.7ltr. I drained the transfer case when removing. Do I need to add fluid back to the transfer case or will the pump from the transmission pump it through the spacer into the transfer case?

The transfer cases I've seen need to be manually filled, usually with 2 quarts of ATF. I'm not familiar with your Tahoe, however.

Thanks for your help... I found out that it does initially need to be filled and it holds 3.5 qts... The weep hole lets the fluid gradually flow back and forth as needed...

Both transmission and differential use Dexron-III but the systems are desinged to be sealed from each other.
The have significantly different operating parameters and service intervals, fill and drain styles. These are independent systems.