Auto gearbox modification

[BUSHWHACKER]

Aiming for a manual override on the automatic gearbox - best of both worlds

Should in theory be pretty simple. Off to speak to an electronics guru at work now to see what he says...

My Celica is semi-automatic (Tiptronic) Fully auto or select 'D' then across into 'manual mode' and change up and down gears with buttons on the steering wheel.
When driving in maual mode and I approach a junction, the transmission automatically downhifts back to first which is a nice feature.
I'll see if there's a wiring diagram for it on my workshop CD, might be of some use to you whiz kids.

[adpsimpson]

To keep the thread updated, he suggested putting a diode between the solenoid output (lockup out) and earth, as the solenoid may be causing inductive spikes which could keep the mosfet open, causing the NOR gate to behave badly.

Makes sense, I'll try it this evening and post back.

Apache, did you ever build your circuit, or just install a simple flick switch? I've got that in just now and it works, but isn't exactly nice at low speed.

[adpsimpson]

Aiming for a manual override on the automatic gearbox - best of both worlds

Should in theory be pretty simple. Off to speak to an electronics guru at work now to see what he says...

[BUSHWHACKER]

Blimey!
Wouldn't it be easier to buy a manual gearbox?

[adpsimpson]

Andy, here's what I've managed while trying to mimic your setup.



I've made a slightly different circuit, using just a triple NOR gate and copying your setup with the switch, debouncer and flip flop. I've stuck some LEDs on to tell me what's happening, including one in the switch (LED1 in the diagram), one for each of solenoid 1 and 2 (LED2 and 3), one for when the vehicle decides to go into lockup normally (LED4) and one for when lockup is active (LED5). I've not go the brake signal in there yet, but it will go to pin 4 of the NOR gate.

When I short the lockup input and output signal together and don't provide the 12V input for the solenoid, the LEDs all do what they're meant to. Activating the override lights LED5 in 3rd and 4th gear. But when I set it up as in the diagram, I can drive away normally, engage the override, and it works. But I can't then disengage it. The button still seems to be working, but the solenoid 1 LED lights dimly no matter what state it's in, and the relay stays activated.

I suspect I should be limiting the current through the lockup solenoid as its resistance is only about 12 Ohms. I think the problems are because I am basically shorting 12V to earth while it's active. Did you have a resistor between the 12V supply and the solenoid? Any other ideas what could be happening?

[Apache]

TBH, no.

I kind of got sidetracked, and my winter 'fiddling' time evaporated! It's another of those "will get round to it one day" projects.

However, the simple lockup switch is dead easy. Matt F's site has data on the ECU (exact wiring depends on which one you have) and it really is just a simple matter of applying 12v to the lockup solenoid / disconnecting the ECU output.

Mine is still wired in and still used on long A-road trips when the traffic speed is up and down between 40 - 60mph. The 3.0 is completely happy in top / lockup down to 40ish on the flat, and it does seem to help mpg a little. Kickdown still works, and feels like a manual box as the downshifts / upshifts are harder because the TC is locked up.

[joedude]

Any new developments on this?

I'm thinking of installing a simple lockup switch in my surf cause I'll be doing an 800km trip where I'll be pulling a trailer with all my stuff in it. (not sure on the weight, but It'll be plenty) I don't have the electrical knowledge to build that circutry with the bells and whistles mentioned previously - As long as I remember to flick the switch off when I stop!

Any suggestions on this? I figure the lockup switch would stop my trans from switching in and out of lockup which should avoid an overheat potential right? Also won't have to do the trip with OD OFF, therefore increasing my MPG?

Thanks!

[KERRSURF]

sounds promising Andy, let us know how you get on.

[Apache]

Have you thought about putting an standalone tranny computer as I'm doing? It's cheap and you can configure almost everything...

David

No. If I couldn't do it myself, I wouldn't bother to be honest. I'm basically only doing it for interest's sake, because I like messing with the electronic side of things.

One thing I have noticed though, even with the just the basic manual lockup switch connected, is that I do get a noticeable improvement in fuel economy on long runs.

Normally when I fill the tank to the 'clunk' on the pump, I get around 50 miles before the fuel gauge needle gets to the last mark on the scale, using the lockup in 3rd and OD down to about 1500rpm (use the OD button to shift between the gears) I managed 65 miles to the same point! I haven't been able to do a definitive comparison as yet as I dont do too many miles, but on my next trip up 100 or so miles of the A49 and back, I'll check it again.

[Blizzard]

Hello,

Sorry for not replying before.

I only know how the auto tranny works "phisically" but I cannot say anything more as I've never driven an auto Surf (And I'm swapping mine haha).

I readed in this thread that the stick can control 1st, 2nd, 3rd and no O/D. This is not true. You can drive the truck with only the stick but the shift is 1st, 3rd, O/D. This is like when the two shifting solenoids fail, the 2nd can't be selected as the solenoids 1 and 2 are ON-ON.

Have you thought about putting an standalone tranny computer as I'm doing? It's cheap and you can configure almost everything...

David

[MattF]

I was actually considering multiplying up the pulse frequency from the speed sensors (there's two of them both feed the ECU) and fooling the car into thinking its going faster than it really is - which is what you were vaguely alluding to - but that would then throw out the speedo too, and would only give you lock-up in OD.

Yup. I'd overlooked that 'nugget'.

[Apache]

Not yet. Kids are off school, and I've been busy with them, and off on hols tomorrow. I will post back when I get things moving again.

[KERRSURF]

Ant further progress Andy?

[daithediver]

Looking forward to full write up perhaps with a couple of diagrams for us thickies who don`t understand the auto box too well.

[Apache]

Hi Apache,been reading this thread with interest,just wodering if you have made any further progress.

Haven't had much chance to do anything other than a manual lockup switch so far. Used it driving to Shrewsbury on Friday, and down to Tony's yesterday. The truck seems happy enough down to ~40mph in OD in traffic on A roads that varies between 40-60mph, and with OD off, it locks and runs at about 1500rpm at ~30mph in 3rd. Its comfortable there too, and pulls fairly strongly from that speed when you put you foot down.

I reckon fuel consumption is improved, especially on long 40-50mph runs locked up in OD.