23. This is the Powertrain Control Solutions (PCS) automatic transmission controller, and it's mandatory for this swap. PCS sells these units through distributors like Brian's Truck Shop and DeStroked. Quite simply, this unit controls operation of the electronic 4R100 transmission. It came with outstanding instructions, detailed schematics, and a DVD for programming. Zuccarello mounted the PCS controller (and the DeStroked tachometer adapter) inside the vehicle so they would be protected from moisture. The transmission controller comes with basic programming to make the transmission functional. Zuccarello will then work with Brian's Truck Shop to fine-tune the controller for his application via software.