The speed transducer for many GM applications screws right into where the speedometer cable goes--in this case, on the driver's side of Cheap Street Chevelle's B&M TH350 automatic trans (photo 2). Once installed, screw the speedo drive cable, in series, to the other side of the transducer. However, the speedometer on our Chevelle is broken, so we didn't install the cable. We left the cap on the end of the transducer and tie-wrapped the cable out of harm's way (photo 2A). With the dyno, the Chevelle now has an accurate speedometer. If you have a race car with no speedo hookup on the transmission or anywhere else, then DynoLab offers an optional photo speed transducer. It uses an infrared light beam and reflective tape on the surface of the driveshaft to measure vehicle speed.