How does a computer control an automatic transmission?

How does a computer control an automatic transmission?

And how do you spoof it to manually control it more like the automatic transmissions of old?

I have a need for a very small FWD automatic transmission that can be spoofed into working well with a completely different type of engine.

So I need to know which ones can be controlled and some ideas of if I have options (or there's only one in the whole wide world) that might be very small, light and "might" have the option of an LSD if I later deem it to be necessary.

I'm not sure an LSD is necessary, but that's a topic for a different thread.

All I need to control is 110ish ft. lbs of torque in a "vigorously driven" environment.

It actuates solenoids. Figure out what you need to apply, power those solenoids.

OK maybe I need to say it more clearly, is there an easy way or an already devised way to put an automatic transmission in a car without a computer that doesn't require me to reinvent the wheel. They used to do it.

Yes, ready made or something simple that even I can do and doesn't require me to learn a degree in transmissionology. (Dr. of TMO won't fit on my business cards)

you can buy aftermarket trans controllers for the Domestic auto transmissions/ GM, Ford, and Chrysler all sell plug and play setups to put their rwd transmissions in older cars.. some of the aftermarket EFI setups also control auto transmissions..

i've also seen- on either the Chumpcar or LeMons forum- people that have wired up toggles for each different shift solenoid...

You seem to be overlooking the fact that MOST fwd transaxles until the late 90s didnt have a whole lot of computer control, and most from the 80s had none at all. Will none of those transmissions work?

What is the engine?

And, it really varies by transmission. The computer for a 1998 chrysler 604 is pretty complex. The computer for a 1998 gm 4t60e is not very complex. We really need more info.

I thought all automatics had been computer controlled since the 80's so I was presuming there would be no manual controlled FWD transmissions available. I'm glad to hear I might have some choices that require minimal adaptation.

I'd love a kickdown lever type implementation if I can. Once upon a time I had a transmission computer malf and it seemed to default to wide open throttle settings so shifts were very abrupt and very high even under light throttle which made the car very hard to drive until I figured out the problem so that's what I've been presuming would happen unless I found a way to make the transmission think it's connected to it's designed engine.

It's a carb'd bike engine with basically only spark control done by a computer. I can easily rig some sort of throttle position sensor, but I wasn't sure if that was enough.

GM didn't go to computer controls across the board until about 95 or so- but they had computer controled transmissions at least as early as 92 in the AWD Astros and LT1 Corvettes. i don't know about the fwd transmissions, except that the 93 Lumina i had still had a tv cable but the 94 i had was fulley electronic. the trans in my fwd 97 Monte Carlo is electronically shifted, but still has a vacuum modulator on it for some reason..

in the world of small fwd- i'd say look at a late 80's/early 90 s economy car of some sort. something like an early Geo Metro that had a carbureted engine.

Some Dodge Neons ran the three speeds ( hydraulic) up till 2002?

I have heard a story of someone making a (min van) Chrysler 41TE work in a full manual four speed type operation, he used a shifter with manual contact switches for the different gears (used to control the solenoids in a on/off system). He said it worked but was a rather harsh shift. Since the Chrysler 3.8L (min van) makes well over 110 HP this trans should hold up for your use.

One thing you might want to look for if you want to use a electronic trans is the "whats on when" chart to help find a unit that could be controlled in a manual sense.

Donebrokeit has the right idea. I'd also suggest looking at, say, '80's or '90's Geo Metro or similar slushboxes. Honda boxes might work but the engines turn backwards. FWIW, car-part.com shows a bunch of A/T 1.0 3 cyl Geos here in the southeast, the boxes are anywhere from $125 to $350.

Even when computer controlled, many slushboxes have a manual control where the shift lever moves a cable or rod that moves a spool in the valve body to produce a shift. Some of them have an electronic override which prevents the transmission from going into 1st at, say, 80 MPH which could lead to a bit of a problem.

Assuming you don't HAVE to mod a gearbox you already have, you could just buy one of those "tiptronic/sportshift" automatics that already have electronic sequential shift control.

I have a friend trying to make an automatic into a manual(ish) by using push buttons to actuate the electronic shift solenoids. Kinda like a paddle shifter.

FWIW, I'd see if you can find a local transmission shop that will actually let you talk to a tech. This may be difficult, but I'd bet offering to buy the guy lunch for his time would be worth the $10 investment. Just an idea...

In the 80s, the most computer control anything usually had was an on/off torque converter clutch solenoid.

Also, like i said, all computer control is not created equal. an 89 a604 chrysler has a MUCH more complex control scheme than a 99 4t60, for example. For example, a 4t60 is basically an old-school trans with the computer control being basically a PWM line pressure solenoid, some shift solenoids, converter clutch solenoid, etc.

a 604 is what's known as a 'clutch to clutch' shifting trans and the computer actually monitors the 'fill/apply time' of each holding element by timing and monitoring changes on 2 speed sensors (besides the vehicle speed sensor) and adapts how it modulates each shift solenoid based on the timings it took. It takes all that to make the thing shift right, and it adapts for wear in the same way so shifting stays roughly the same until the hard parts are way out of wack. Also, the converter solenoid is one of the shift solenoids. i.e. its either a shift solenoid or a converter clutch solenoid depending on what position each of the other solenoids is in. TRICKERY!

So yeah, you can shift a 4t60 with switches, but you cant do it on a 604 without burning it up in short order.

So it DEPENDS.

Thats why i think you should really stick to purely hydraulic controls, because otherwise you're making a lot of work for yourself. It's a steep learning curve.

MegaSquirt has the capability to control those many of those types of transmissions.

MegaShift.

Sounds like the megashift is the hot lick.

Huh. Wasn't aware the Megashift existed. I knew Megasquirt could control transmission functions but didn't know they were offering a standalone also.

I keep wanting to MicroSquirt my XS650. One of these days...

I think megashift is a neat idea as long as you dont try to use it on a 604. plenty of other fish in the sea. What's the engine again?

Not a car engine.

does it need to be a 4 speed? If not use any 80s 3 speed.

carguy123 wrote: Not a car engine.

well that clears things right up.. i say we should all taylor our answers based on the engine being a 5hp Briggs off an old push mower and go from there.

Making an electronic transmission perform without the computer is not cool. There are tons of FWD transmissions out there that have both electronic and old-school configurations.

Toyota's A130 is a good choice. They sometimes have governor issues but its pretty easily repaired with a sleeve kit.

If that doesn't suit the bill, anything on THIS page should be supremely easy to adapt, lightweight, and based on dead-nuts reliable (and cheap) parts.

Im not trying to be rude here but i feel like this thread started off with a bad idea and then the OP withheld the necessary info for us to make truly helpful suggestions.

Im not really in it for the suspense when i browse here so good luck with your 'non car engine' project.

novaderrik wrote:

carguy123 wrote: Not a car engine.

well that clears things right up.. i say we should all taylor our answers based on the engine being a 5hp Briggs off an old push mower and go from there.

That'll work. There's no correlation between the engine and the transmission in this case.

Vigo wrote: Im not trying to be rude here but i feel like this thread started off with a bad idea and then the OP withheld the necessary info for us to make truly helpful suggestions. Im not really in it for the suspense when i browse here so good luck with your 'non car engine' project.

I didn't withhold anything, the engine isn't relavent to the question I asked. I want to know about transmissions and not about an engine.

"I have a need for a very small FWD automatic transmission that can be spoofed into working well with a completely different type of engine. "

I want a very small, more than 3 speed automatic transmission that I can ideally control it manually. I was trying to learn enough auto transmission speak to decide upon where to begin looking.

My fear was that all the automatics had progressed to the point that they all required a computer and if so I was wondering what I had to do to spoof it into thinking it was working with the engine it was designed for.

I want dead simple & dead cheap cause this is a toy and I want to put as little money into it (and as little time figuring things out and trying to make it work) so I can begin playing.

So once again this is not about any specific engine or manufacturer I am trying to see how to make an automatic transmission work with a completely different engine.

Can I do it with a TPS and a vacuum line? Do I need to add a speed sensor or do I just have to go with an older one which makes it tough to find more than 3 speeds.

As far as capacities I said in the original post : "All I need to control is 110ish ft. lbs of torque in a "vigorously driven" environment."

geo metro 3speed auto only has three wires(12v switches) needed to control the solenoids line pressure is via a cable you tie to the throttle