All the OBD2 engines from 1996 on require a vehicle speed sensor. The engines up to 1995 can also benefit from an SSK5, most conversions idle and perform better with one installed. This hall effect speed sensor bolts to a Vanagon transmission and the magnetic ring to a cv joint flange. It has 5 pulses per axle revolution which closely approximates the Subaru pulses per mile. Fits Syncro, 2wd manual and automatic.