manual control of auto trans valve solenoids ?

[amnonholland]

Hi all

i have a 1994 1.8 v6 k839 ecu, 4 speed auto, running sequential multipoint lpg

im interested in manually controlling the automatic transmission. The trans shifting is controlled by 3 electronic solenoids and 1 for the torque converter lockup. would it be possible to splice into these after the ecu to be able to manually shift the trans similar to a tiptronic gearbox.

i have the k839 ecu and cant identify the ecu pinouts for the solenoid valves as compared to the chilton manuals on this site (1995 and 1992 under auto-transaxle).

Would there be problems associated(undue strain placed on auto trans) with manual shifting of the gears?
i dont think so, but manually controlling the torque converter lockup would/may prematurely wear that "clutch"

eventually i would make a shifter of some sort that would control the gear changing

from the chilton manual, what i have inferred about the shifting control would be as follows

Gear 1 2 3 4
2E 0 V V V
2G V V 0 0
2I 0 0 0 V

2E, 2G, 2I are the shift solenoids, V is the battery voltage and 0 is zero volts.

would these solenoids require continuous batt voltage or a pulse to actuate?


any comments/ guidance and help would be appreciated

and yes i may do the atx to mtx much later down track when funds/ time permits
atm "tiptronic" shifting would be nice

[PoisonDrop]

When I did my BP swap. I toyed with doing the tiptronic thing, but in the end, it was way too much trouble to bypass the ATX computer. I figured if I was going to do all that work I'd be better off just doing the MTX swap in the first place. It wasn't expensive at all to get the parts for the MTX swap. Your situation may be different, though.

Just my .02

[PoisonDrop]

After re-reading, I thought I would go a little more in depth about your idea...

To operate something like this, you absolutely MUST use some sort of a circuit with an programmable IC chip. This circuit must have a way of keeping track of which gear you're in, and accept input from paddles or push buttons to shift up/down. Also, you must be able to lock out the shift buttons when you aren't in drive. All of this would require who knows how many sensors and such. Just as well, each gear seems to have a sort of combination of voltages applied to multiple wires in some cases, so there's definitely a need for some kind of logic circuit there. (By the way, this is exactly what the ATX computer does, minus the push button input.)

So you see, unless you have the skills to design and program a circuit board for this task, then it's just not possible. There are too many variables involved, hence the use of a separate ATX computer.

The only way I could think to avoid this is to open the ATX computer and hack it so that you can tell it when to shift. You can't just control the solenoids by themselves. In order to go this route, you would need to gain access to the schematics for the ATX computer (which I'm sure Mazda isn't about to just give to you).

Even if you did have the means to create something like this, it would probably take quite awhile and may end up costing more than just doing the MTX swap outright. And of course, there's always the risk of hurting your transmission...

[amnonholland]

thanks for the reply and input !!

yes it would require a programable PIC chip or some logic circuit if i were to pursue the the paddle shifting input or similar.(which i would like to do). But for preliminary and experimental phase, 3 toggles switches would do.
it may not be as hard as you make out. All it would require is splicing into the wire (3 wires) between the ecu and atx. An "overide" switch would be installed between the ecu and atx to bypass the ecu for manual control, but would resume normal auto operation when closed.

why would you need any sensors?

Voltages to be applied to the solenoids are only battery voltages.

why would there be so many variables? it would just be a matter of applying the right voltages to the right 3 wires. ( 3 variables) i didnt think it would be necessary having safety mechanisms to stop shifting whilst in park, reverse, neutral etc. It would be no different to a manual transmission, with respect to shifting without using clutch or some other stupid action.

Why cant you just control the solenoids by themselves??? thats what the atx does. The voltages and position(gear selected) of the solenoid are specified in the chilton manual under auto trans

All i need is the ecu/at pinout for the k839 module. The wire colours (as displayed in the chilton 1995 manual were inconsistent with the pinout of my 1994 k839 ecu). I just need to be able to identify the 3 correct wires.

BTW the ecu has the auto trans controller built in, right ?
then what is the computer box (looks like a ecu) sitting under the stereo with a wiring harness of about 8-10 wires ?

thanks in advance for advice and comments

[PoisonDrop]

why would you need any sensors?

So you don't hit the wrong switches at the wrong time and mess up the tranny. If you trust yourself not to do this, then you don't need any.

why would there be so many variables?

There are only variables if you were to use an IC. If you use toggles, all the variable stuff would be controlled manually.

Why cant you just control the solenoids by themselves??? thats what the atx does. The voltages and position(gear selected) of the solenoid are specified in the chilton manual under auto trans

You can if you want, but to shift, you'd have to remember the different combinations of voltages, and if you mess up, boom. No more tranny. You may just kill a solenoid, I don't know. But I don't think it'd be good.

BTW the ecu has the auto trans controller built in, right ?
then what is the computer box (looks like a ecu) sitting under the stereo with a wiring harness of about 8-10 wires ?

That's the ATX computer.

I'm not saying that it can't be done manually, just that to do it that way would put your tranny at risk. Paddles or buttons are safer because all the different voltages and such would be automatic, and you wouldn't have to remember them. SO MUCH EASIER to operate IMHO, plus less chance for completely screwing your tranny.

And for the pinout...have you checked the online manual?

[amnonholland]

i agree, there is too much of a risk remembering voltage combinations.

What about having 4 pushbutton switches setup so each controls the respective gear. you wouldn't have to remember any voltage combinations. The type of switch would operate so that one of the 4 can only be selected at a time. Would it be possible to wire with relays, etc ?

I looked at all the online manuals and the wiring coloring is inconsistent with my ecu.

[PoisonDrop]

In theory, yes. But the automatic transaxle is a complicated system, and I can't even begin to tell you what all those other wires do. It's not just about human error. I'm sure you can do without some of the ATX computer's functions (such as hold). But as I said I don't know what all those wires do, and it may not work unless some (or all) of them are hooked up.

I'm just saying whatever you try be careful. Like I said I looked into this awhile ago, but the MTX conversion was just less hassle.

If you need more info, just look at the online manual. There's a little over 300 pages of info on the ATX alone. There's a pinout for you as well.

[Newfie_dan]

shift solenoids operate 2 ways 1 pressure activated by atf pressure, or 2 operated by voltage from the ecu. Its a simple electric over hydraulic setup but to answer your question about manually activating the solenoids its not as simple as 1, 2, 3 switichin solenoids on or off. Look at the hydarulic schematic or JIC diagram of the valve body. You need a vss input, ambient temp of the oil, pressure readings and more to best determine what are good shift points not to mention the converter lockup, mess that 1 up and you will be melting the torque converter. Furthermore to add to your query the solenoids are not run just off 12 volts input, some run off 7 volts & some off 24 volts you would not know the operating voltage without more info. The wiring for said shift solenoids also run through the neutral safety switch which prevents any shifting of the solenoids when in park. It is possible to program a small piggyback module to control shift points but you would need the inputs that I mentioned earlier as well as safety shut downs to prevent transmission damage. I am a wiring and hydraulics troubleshooter and have done many different setups for everything from winch gearing controls to full on automatic transmissions that are controlled via a piggyback computer.

[amnonholland]

thanks for the explanation

ive given up on this project as my transmission is dying.
it keeps slipping and reving high and only stops slipping when torque converter engages.
It might as well be a CVT transmision now since revs drop down as car start to go forward.

Will end up having to a ATX to MTX swap soon when i can afford a donor car.

Will changing the fluid stop slipping ?
its only a light brown colour and transmission was replaced bout 30K ago according to previous owner

[Newfie_dan]

Proper fluid level and proper fluid will help but slipping usually indicates worn out clutch packs or really bad pressure from the fluid. Basically the shift solenoid opens the passage to the clutch piston and the pump applies pressure to a clutch pack compressing the discs inside normally there is a gap between the clutch pack which is just a friction disk with teeth on the outer diameter and a metal plate with teeth on the inner diameter sandwiched together and layered disc, friction disc inside the piston chamber. When its released they turn freely from eachother and when compressed the grab and turn esentially locking the outer gear to the main shaft. Once that friction material wears off there is no more grip hence the slippage. Bad or worn out fluid just makes that friction material wear off faster and it can't cool or lubricate as effectively as good fluid. Proper fluid and filter changes make sure you get the max life out of the transmission and valve body. The biggest problem faced by the atx is cooling in warmer weather conditions especially stop and go traffic. The factory cooler on these atxs and the ones in the ford probes/mx-6s was the weak point it was nothing more than a simple tube, no cooling fins to speak of and very ineffective temp control of the atf. That allowed it to burn up and thereby cause valve body problems and premature transmission failure. It can be fixed simply by putting a better cooler on there and an inline filter to help the regular transmission filter get the junk out of the fluid. To check the level properly you need the car running at idle until you hit operational temp, once thats reached shift from P to 1 and back again then with the car running pull the dipstick and check your level. FYI brownish fluid on the dipstick usually means much more cruddy fluid in the transmission pan, so change the fluid/filter top it off and then flush it your self by pulling the cooler line off the top of the tranmsission cooler and then attach a hose to the cooler and to a empty bucket, have someone fill fresh atf into the dipstick tube with a funnel while you start the car and let the old junky fluid drain into the bucket until nice new red atf comes out. It wont take long to accomplish this. You will need about 4-6 L of atf total.

[amnonholland]

wow! thanks Newfie_dan for all the info.

I had trouble disconnecting the cooler lines to drain fluid.

So i dropped out pan from bottom with fluid into tray. Only 2 litres did flow out. fluid in bottom of pan was reasonably thick. There also was a large amount of metallic particles adhered to the magnet. I cleaned out pan, reinstalled and added 2 litres of ATX fluid. Barely slips at all now( not sure how long this will last for). Could maybe last several months before i do the MTX to ATX conversion.

[Newfie_dan]

no prob anytime