Friend wants to run a 904/998/999 based lock-up trans in a 66 Dart behind a mild 360. Main question is - do all lock-up 904's shift into lock-up "mechanically" - referencing high gear applied and governor input, or are there any lock-up 904's that have an electric solenoid that dictates converter lock-up? I thought I remembered seeing a lock-up 904 with a connector at the left rear of the case for a lock-up solenoid wire. Trans didn't have a trans brake in it, before any one asks. Is there an "electric" lock-up valve body - if so - application?

And does anyone make a "budget" converter for this trans that has a little better stall and would live behind a 350 hp 360?

Sure the later ones use a solenoid in the trans. All the early ones when they first came out in Mopars were hydraulic as I remember a 1979 Aspen I believe that was all hydraulic. I dont remember what year they started using the solenoid in the valve body so the PCM could control lock-up but I know my dads 88 truck had the electric lock-up solenoid in it as that year just had a one wire plug on the left rear of the trans main housing. The solenoid just controlled a bleed off (vent) of fluid pressure to the lock-up valve. John Kunkel will know which year they started with the electric solenoid in the valve body but I dont remember myself right now. Ron

The case he is using is a 999 out of an 83 Imperial. It doesn't have a lock-up solenoid on the valve body.

Info I'm seeing is that it's an 87 up valve body needed. Maybe someone will weigh in and confirm.

That, and about the torque converter options.

All 3-speeds lock up mechanically...some later transmissions in the 904 family have an electrical connection but it's for unlocking the converter only.

I cant see how that can be since the solenoid has to close the bleed (vent) in order for the lock-up valve to move so the converter can lock-up. I would consider them as an electronic controlled lock-up only because they have the PCM controlled solenoid. Even one of my Mopar 1986 training books calls them a "Electronic Lock-Unlock converter". Ron

Can you elaborate on this a little, John?

What we are trying to accomplish is to protect the lock-up clutch during heavy throttle 2-3 shifts. The full mechanical L/U valve body simply locks up the converter when it shifts into direct over X output shaft speed, which is probably about 45 MPH. The way I read the flow charts - no, you can't use the solenoid to lock the converter at will, as in 1 or 2 - it must be in direct to apply L/U. But can't the solenoid be used to selectively control L/U in direct? It seems to just bleed the signal pressure off going to the lock up valve to prevent the L/U valve from sending apply pressure to converter. We would like to be available to control L/U with a vacuum switch, toggle switch, or both.

So is this possible, or am I missing something here, such as also losing apply pressure to the front clutch, etc.

Thanks for any input you can provide.

I could be wrong...disconnect the wire and see if it locks up.

Cop spec M bodies had an electrical part throttle unlock solenoid that allowed the TC to unlock based on throttle input. Lockup functioned just like the civilian version.

So, do you apply power to close the solenoid and enable lock-up, or apply power to open the vent and disable lock-up?

It has to have a few things before it will lock-up when it uses the solenoid. As John says it is done mechanically and electronicly when it uses the lock-up solenoid. One of my training books says it started the electronic lock-up/un-lock in 1986. The trans has to shift into second gear so the 1/2 shift valve will send line pressure to the lock-up valve and also past the lock-up solenoid where the pressure is vented until the engine controller (PCM) decides that the vehicle is going fast enough , the eng is over 150 degrees , the PCM knows the eng is not at idle and knows the TPS posistion and the eng vacum is correct for lock-up. Also the trans has to have shifted into third gear so the 2/3 shift valve will send line pressure to the Fail Safe valve and cause it to move over. Once in third gear and the Fail Safe valve moves over and when all the criteria's are met the PCM will ground the lock-up solenoid and cause the line pressure from the 1/2 shift valve to move the lock-up valve over which then lets line pressure from the rear clutch circuit push the switch valve over. When all that happens the line pressure from the rear clutch circuit goes through the moved over lock-up and fail safe valves to the switch valve which moves and redirects line pressure to the converter in the opposite direction which then pushes the lock-up piston in the converter on and locks up the converter clutch. Does not matter if it has what they call a part throttle unlock relay as the relay still powers the lock-up solenoid on or off as the relay is still controlled by the PCM to control when the converter locks or unlocks.
Solenoid off means the line pressure from the 1/2 shift valve vents and will not move the lock-up valve so the converter will not lock-up. When the solenoid is turned on by the PCM then the vent is blocked so pressure builds to move the lock-up valve over and gives you locked up converter. Ron

This probably answers my question - I had already studied the hydraulic charts and knew the fluid side of it. Your training books must be for the later 2 wire solenoids, since you mention the PCM switches the ground to the solenoid. Both the V/B's we picked up yesterday have 1 wire solenoids that ground through it's mount, and would need 12V+ power applied to function. We will probably just wire a toggle switch supplying power and see what happens once it's in direct.

Thanks for the replies

Actually you are right as the 86 models and some other years do have one wire to the solenoid and its a 12 volt wire. The PCM is controlling the relay coil winding ground which in turn send 12 volts to the solenoid. Sorry as I am used to the PCM controlling the ground and forgot its the relay (trans lock-up or also called Part throttle un-lock relay) ground that the PCM controlls. Ron

Here's a wiring diagram of the unlock solenoid. Power to the wire unlocks the converter.

Here are some pages from one of the 86 training books I have from Dodge. This is a brief wire diagram in it. Ron

This page says that the relay which controls the solenoid locks and unlocks the conveter. Ron

This is from the same book as it shows the solenoid venting in unlock. Ron

And this shows the solenoid on (not venting) and the valves all in the lock-up possition which have the conveter locked. These are all from a training book that I got at training at the Dodge dealer in 1986. Ron

I can tell you this,I removed the computer from my 88 d150 with one wire lockup.
Now there is no lockup.
If it was locked up it would most likely stall or near stall the motor at idle.

Thanks for all the replies.