The purpose of the relays housed with trans components-automatic is to transmit and intercept data from the transmission and its components to the ECM of the vehicle. If the relays aren't processing the information clearly and the sensors are off, your transmission may lock into certain gears or start slipping out position.
If there are problems with the transmission, you vehicle might show it several ways. You may have trouble downshifting in your vehicle, or it may not shift at all when the transmission should. You might hear grinding noises, and you may feel the car shudder when the transitioning between gears. Check StockWiseAuto.com for replacement parts.