Where is the backup light switch located on a 1989 GMC pickup with a manual transmission?

You should have one of these three Transmission's HM290 (Hydramatic), a 5LM60 (Muncie) and a NV3500 (New Venture).
It should be located about 3/4 of the way towards the rear. On the drivers side where the shifter comes thru the floor. An should have about 10 gauge wires leading from it. Good Luck and Remember.
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