Suzuki 4WD Club of Victoria

MYSTERIOUS 4th switch/sensor .
Hi Suzuki gurus , I am in the process of putting a refurbished Gearbox in my 85 Sierra with the help of Luigi .

The second hand gearbox i bought which Wayne kindly put new bearings in has a mysterious 4th electrical switch coming from it .
Wayne nor i have ever seen this 4th one before , does anyone know what it might be for .
I actually dont know what the 3rd one is either . I assume there is a 5th gear , Reverse and ????
I'm just curious, not concerned.

Perhaps it detects the presence of sand ? a sandswitch ? hahah , Sorry , dad joke .

Cheers, Richard

I put a 93 box in my 85 Sierra I know I have a reverse because my lights work but other than its not fully wired in and it runs fine.
I would have no idea why you would need anything other than a reverse switch

I believe there are switches for 4th and 5th which control EGR, and obviously reverse. I have a 1987 edition FSM and it doesn't show a 4th switch. A multimeter will tell you which one does what quickly enough. My guess is neutral.