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

Speak to Ray Edwards Simon. He's done a few manual to auto conversions so must know them reasonably well. Also, as you know, he's a clever chap!

Kirkynut

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