Clean it up and you will see four bolt heads where it bolt to the front extension of the transfer case. The vacuum shifter has a fork the fits over a collar that slides to engage and disengage 4WD. When you reinstall the vacuum shifter be sure the fork goes back in the groove on the collar.
Also, when you go back to re-install, I suggest that you carefully inspect the condition of your 4 bolts and be careful when you tighten. I recently had one of the bolts shear off into the nosecone. No fun.