1999 3sp Auto Box wiring questions?

I've just bought an auto box on eBay.

Would I be correct in thinking it is electronically controlled? It has a connector on the selector input plus two other connectors, one has a wire passing into the valve chest and the other to a sensor on the input from the engine.

I presume its something like the later Vitara Autos where Park, Reverse, Neutral & Drive were selected mechanically and the gear (1,2,3) plus the torque converter lockup are selected via solenoid valves in the valve chest?

Does anyone have a wiring diagram - or know anything about them (in terms of hacking / reverse engineering)?

I don't have the ECU for the box, assuming there is a separate ECU - though I imagine I could build something suitable - or even use MegaShift (part of the MegaSquirt family).

If it is a properly electronic box, it would be useful to be able to lock the torque converter at low speed to give me increased engine braking - potentially make it so that if it is in low range and the throttle is at zero, it locks up?

Si

Ray & I are quite good friends! He's fantastic with anything mechanical - but looks at me blankly as soon as I even think about electrickery, let alone computers!

I think, if I mentioned reverse engineering and building a shift controller - his head would start spinning!

Si

yes they do have an ECU but I dont have a manual / diagrams, but i have an auto jimny sat here

i no nothing about auto jimnys and ive not driven this one yet, other than its got overdrive

if you need me to chase some wires or have a look at anything, but im sure you would be able to make it work stand alone, as i can't imagine them being canbus as im sure you no complicates things.

To add a bit more they are a 3 speed auto with switchable overdrive. They are electrically controlled and have a lock up torque converter. They won't change into overdrive, or lock up, until they are warm. Also if you fit different gearing, or bigger tyres you need to fit something that accurately tells the box the speed you are doing otherwise the changes are all over the place. Like most auto boxes they are very sensitive to over temperature, so a good cooler is essential. Sorry I can't be more technical about it, but I guess every little bits helps!

Thanks for that.

I presume 3 sp + Overdrive can just be treated as 4 speed? Or is the Overdrive weaker than the other gears and have to be used with more caution?

Do any of you know which solenoid corresponds to which gear?

After market shift controllers generally just use the throttle position as a measure of torque plus the speedo to measure road speed - then have a look-up table which uses both of these to select the specific gear

They then override this with max and min gears at different temperatures, whether the box is in High/Low etc.

I plan to build my own shift controller just using a microcontroller. That will allow me to add Torque Converter lock up and the lowest gear if the transfer is in low and you lift off the throttle, then unlock when the speed is below a threshold. this should give me the maximum engine braking for hill descents. In High range, it will select the highest gear and no TC lock for zero throttle - to allow it to coast.

Si

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.

i have jimny manual
just mail me, i send it email.