The A340 transmission features two speed sensors, The input speed sensor on 2WD models is installed at the front end near the bellhousing while the output speed sensor is installed at the rear on the extension housing while in 4WD models, it is installed at the front left corner of the transfer case. To replace a speed sensor one has to lift the car and support it on jack stands and remove the electrical connector from the sensor that is being replaced. Secondly, then you need to unscrew the retaining bolt and pull out the sensor along with the old O-ring. When installing the new sensor be sure to apply clean automatic transmission fluid on the sensor O-ring. The process of reinstallment is the reverse of the above sequence, while confirming the condition of a tightly screwed retaining bolt. Like the A750E and A750F, the 2WD and 4WD also have input speed sensor located at the left side while output speed sensor located at the right side. The replacement process is identical, Lift the car and then remove the electrical connector and then the retaining bolt and sensor of the CAT-019 refer to EL-037657 To replace the current O-ring discard it then coat the new O-ring with ATF and reinstall the unit while tightening the bolt in a proper fashion securely.