My new replacement piston arrived yesterday from RockAuto. Nice and shiny, but I noticed the gear housing that meshes with the parking brake adjustment screw isn't installed. I couldn't find anything in my service manual about swapping the part over. Any one face this issue? Any pointers would be much appreciated.

I am holding the old piston with the gear mechanism for the adjustment screw.

 

Solved my question. Anyone doing this in the future, remove the one-way valve on the face of the piston. I grabbed a #8 machine screw, about 2" long and tapped out the gear mechanism, using a hammer and light taps. The internal parts slid out easily .

There is a o-ring around the part, waiting to see if my rebuild kit incoherently part. I imagine i will be able to press it into the new piston with a c-clamp and a long socket.