1999 3sp Auto Box wiring questions?

I only know from my own experience about the overdrive in that effectively it is a 4 speed box. I'm not aware that 4th is any weaker than the rest of the box, certainly I've had no problem and have used it off road with a rock lobster transfer box in all gears.
What you are proposing sounds excellent and it will be interesting to see the finished result.

I presume that the normal selector just chooses between 1,2 & 3 and that there is a separate switch for Overdrive?

Will it let you select OD in a lower gear - i.e. is it genuinely an overdrive or just a higher gear?
If so, can you use it as a sort of inbetween gear - to give you a gear inbetween 1st and 2nd for example?

Si

The selector has L ie 1st, 2nd and D which is really 3rd and above. There is a separate switch on the gear lever for o/d on and off. Really though, as you say it's a 4th gear as its not selectable for say 1st or 2nd to give a split gear.
Like most unaltered autos it will only change down when the speed Is right, rather than when you might want it to. I think though the o/d will come out at any speed, but I'm not totally sure as its not something I do very often, although I do switch the o/d off for hills to stop it shunting between gears.

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