The invention comprises retrofit kits for power impact tools. The retrofit kits adapt modular control apparatuses to power impact tools that where not originally manufactured to receive a modular control apparatuses. The retrofit kits comprise a modular control apparatus and at least one fastener. The modular control apparatus may be specially manufactured to adapt retrofit tools or an adapter may be included in the kit. Adapters intercept the energy flow to the motor of the tool and re-channels the energy flow through a modular control apparatus, which then controls the flow of energy to the motor. The retrofit kit may include instruction sheets describing and illustrating the methods of using the retrofit kit.