GM 3938481 Switch Assembly, Back Up Lamp

On 1975-81 models with column shift automatic transmission and manual door locks, the back-up light switch is combined with the starter neutral safety switch and is mounted on the steering column under the instrument panel. It is controlled by a carrier tang actuated by the transmission shift tube in the steering column. To install, position the gear shift lever in NEUTRAL, install the switch into the column by inserting the switch carrier tang into the shift tube slot and tighten the retaining screws, move the gear shift lever out of NEUTRAL to the LOW extreme position to shear the switch pin, check operation of switch to verify that the engine will only start in PARK or NEUTRAL, and adjust the switch by positioning the gear shift lever in NEUTRAL, loosening the 2 retaining screws, rotating the switch slightly on the column until the NEUTRAL hole in the back of the switch freely admits a No. 41 (3/32 in.) drill bit to the depth of 3/s in. (9mm), and then tightening the retaining nut. On 1982-87 models with automatic transmission, disconnect the wiring at the switch, carefully pry the switch from the steering column using a small pry tool, set the gear shift lever in NEUTRAL position, align the actuator on the switch with the hole in the shift tube, position the reward portion of the switch (harness side) to fit into the cut-out, push down on the front of the switch, adjust the switch by moving the gear selector to PARK, check the operation of the switch to verify that the engine will only start in PARK or NEUTRAL, and adjust the switch by rotating the housing of the switch all the way toward the LOW gear position (rotate clockwise as viewed from upper end of the column) and move the gear selector to PARK. On cars equipped with manual transmission, the back-up light switch is usually on the gear shifter assembly.