Rear Brake Calipers

The parking brake is built into the caliper and you need a special tool to screw the piston into that assembly. Any auto parts store that rents or borrows tools will have the tool kit. Here is a video that will help with this:

https://youtu.be/hPzxdnLJbhc

and

https://youtu.be/j8YwfSKEzZo

This is a pretty sad state of affairs. Chrysler has always had a better way of doing things that typically benefited the car owner, but here they dropped the ball. GM and Ford used this miserable parking brake design for decades while Chrysler had a much better parking brake shoe setup in a small drum inside the rotor. The rear calipers were serviced just like the front ones. Now GM and Ford finally stopped using that troublesome design and went to the Chrysler system, and Chrysler is using the undesirable GM system.

I attached a picture below of what/how the tool works