user selectable lockup on a chrysler a604 4 speed.
 

ok, i know theres alot of chrysler a604's running around. they are used in almost everything from dodge dynasty to town and country minivans to the cirrus, stratus, sebring, breeze, neon, 300m, etc. they even used in some mitsubishi, i think the diamante and 300gt of certain years.

i hooked up a portable scope i have plus a power inverter to run it to the lockup solenoid put everything on the passenger seat and went for a drive. it seems that my trans sends pulses at 139hz to the sonelod and varies the duty cycle to obtain lockup. this way it can partly lockup the converter, or fully lockit up, or any mix inbetween. if one were to apply 12V to the lockup solenoid, it would probably lockup, for about 3 seconds before it smokes the sloenoid pack! the pack isnt made to handle 12v. i had originally thought the trans just sends a plain old dc power signal to the lockup, but i was totally wrong. im glad i didnt just gung ho it and smoke my converter!

so im thinking it could take a few volts if it was ran through a current limiting resistor. im thinking a lm7805 regulator coupled to a small solenoid and a properly sized resistor to limit current so we dont smoke the converters solenoid. this seems like alot of work though, im not sure how to isolate the DIY mockup from the computers lockup and have both work independantly of each other, but if i could, then the possibility exists to have converter lockup in first gear second, etc. say youre cruiding a country road at 35mph, want to put the converter in lockup in 3rd? its possible. but im not sure how.

wondering if any if you had some insight on this. right now im a little confused as to which direction to go.

Don't know. I did find a web site where a guy had a controller for that transmission, which a part of what it did was what you described. You might try to find that.

Shop Manual
 

If you can get your hands on a shop manual, it should give the schematics for TC Lockup.

For my case, TC solenoids A and B and another sensor (forget the one at the moment) needs to be energized -- which is traditionally done by the Transmission Control Unit processor under the right conditions. I honestly wouldn't know the first thing on how to override the system -- some systems may be easier to deal with. Hill-Logic control tends to be a real buggah if it's involved.

RH77

Well, with the 'teg transmission, you might be able to swap in an earlier TCM that lacks grade logic, then rig up a couple high wattage resistors to look like the solenoids so the TCM doesn't throw an error code. The might part would depend on your transmission having the same solenoids, sensors and such as the earlier version, and the older TCM not paying enough attention to engine RPM vs. vehicle speed to notice the TC is locked when it shouldn't be or is unlocked when it should be.

Are you saying the TC solenoid works by pulse width modulation? onoffonoffonoffonoff?

Wouldn't this quickly wear the TC clutch if it's only partially engaged?

Thanks for the warning to thoroughly investigate the input signal before designing an override; I've been working on this myself. I was just going to wire up 12V directly for an override, but at this point I think my next step would be to cut the wire and extend both ends back to the passenger seat. I can better characterize the signal there.

I don't have a scope, but I have a pretty decent DMM that can do AC/DC voltage/current/frequency, several others without AC and a couple of analog multimeters.

Perhaps the simplest diagnostic tool would be an amplified speaker hooked up to the TCC signal with a current limiting resistor. This would allow me to identify any constant AC frequencies or even transients when switching. If it's just on/off, I'll just hear a pop when it goes on or off. If the voltage comes up gradually (likely because of the solenoid's inductance), I probably won't hear anything.

It's most likely just straight 12V on my car, but better safe than very expensive.

BTW, one way to imitate your 139Hz wave may be to make an audio recording (analog or digital), play it back in a loop and amplify it. Getting the proper amount of amplification might be tricky, but you've got the scope to help with that.

bruce, i was also thinking of the audio idea. i could make a cd with a 139hz signal, and wire one of my channels up to the torque converter, and use the volume control to add the signal.

for testing, if you did exactly as you thought and hooked up a speaker to the lockup line, use one thats maybe 4 inches across, this way you can physically see it move, and feel it move with youre finger. you can tell alot about a frequency without a scope by just feeling the speaker move.

the other option is to use youre fancy multimetre to look at the ohms of the torque converter lockup solenoid. for mine, its like 3 or 4 ohms. if i applied 12v to it, thats like 4 amps, or nearly 60 watts. id smoke the sloenoid. you should look at youre sloenoid resistance to see if it might even survive an encounter with 12 volts.

the tonverter clutch is designed to be slipped at certain rpm's. my car goes through a few lockup modes, including semi lockup, partial lockup, and full lockup. i would think the tcc would be worn but my cars got 180K miles on it and still runnin strong, so i guess slipping the tcc isnt so bad. besides, both sides of the coverter are moving, so were not talking about a 3000rpm differential here as you would see with a manuial transmission, were talking about maybe 60-200 rpm differnetial of speed since both sides of the converter are spinning when it goes into lockup.

Yeah, or you could put together a 555 timer circuit to produce a nice square wave. I seem to recall seeing a DIY servo exerciser circuit (R/C servos move based on a PWM signal) that relied on two 555 timers - one to produce the base frequency, the second had a variable resistor to modulate the pulsewidth. I doubt the raw circuit could provide enough current to drive a solenoid, but I'm sure you could use the output to drive a mosfet or something.

csrmel, you may find this article to be helpful...

Hmmm...I wonder if this would have helped keep my '89 Voyager (junked a few years ago for other problems) from going into "limp mode"?