I have a 1978 hilux with a l43 four speed, when i got the truck the reverse lights were disconnected, when i connect them they are on in every gear but reverse.
Tried to use the switch out of a five speed and it still does the same thing. I know there is some sort of adjustment screw on the bottom of the side case right by the reverse light switch but what does it do, the only other transmission ive seen this on is the l52 and it adjusts the reverse idler gear(whatever that is/does)?

 

How many wires are on the plug?

 

Almost sounds like you have the polarity reversed on the switch. Perhaps there is multiple wires going to the switch. I would take my meter and clip my leads on the contacts of the switch or connectors then I would go through some gears. I would then make adjustments, or change wires until I only had a completed circuit in reverse. Please update your results. My 4runner has aftermarket tail lamps from the previous owner, and the fixtures do not have reverse lights at all. Before too long I will be joining you in this battle.

 

That's where I was headed as well.

Roy

 

Nope, its an open/closed circuit with a hot wire in and one wire out to the lights, only two lights.

 

I mean only 2 wires.