To perform C4 and C5 transmission change follow the steps, First, safely lift the car and support it on jack stands. Release the downshift linkage rod from the transmission downshift lever, smear the downshift lever shaft area with some penetrating oil and leave it for a few minutes then remove the nut and raise off the lever. Disconnect the wire connector of the neutral start switch and pull out the two bolts of the switch then unplug it. For installation, the switch has to be fitted to the transmission with bolts set only loose while the selector lever should be in the Neutral position. Place a No. 43 drill bit into the gauge pin hole about one-half the thickness of the sheet only and turn the switch bolts until tight, then remove the drill. Check that the engine starts only provided that the selector is in Neutral and Park modes. For C3, AOD, and A4LD transmissions, you should begin by removing ground cable from the battery, and electrical connector from the neutral start switch. Unscrew the defects switch and make sure that it is not damaged before replacing it with the new switch then tighten the switch to the recommended torque. Connect the electrical connector and reconnect the negative battery cable and ensure that the engine should start only when the selector is set to Neutral and Park.