The electrically operated lockup torque converter for the A904 sounds too complicated to control with my 1963 Dart.

So, I'm thinking about using the hydraulic-actuated version.

What years should I look for?

How can I tell this transmission from the non-lockup variety?

TIA

--Walt Jackson

What engine are you using, Slant 6 or small block V8?

All you need for the electronic lock-up is a switch to apply 12 volts to it. Those slant 6 electronic lock-up's only came in 1986-7 pickup trucks.

The mechanical lockup came out in the cars in 1978 if I remember right. 1980-up transmissions will have the "wide ratio" gear set for slant 6. California vehicles usually do NOT have the lock-up converter. So look for slant 6 cars from 1978 - 1983. After 1981 the cars with a lockup converter get spotty from limited information I have seen. The truck transmissions may have a longer tail shaft so that will not work in a car.

I do not know how you tell a lockup from non-lockup trannys from the outside. IF the transmission is out of the car you can pull the torque converter off and look for a hole drilled down through the center of the input shaft for lockup equipped trannys.

It's a /6.

Is there any easy way to identify the electric lockup version?

1986 & 1987 trucks only, right?

Thanks.

--Walt Jackson

There will be a single wire going into the transmission case just above the left rear corner of the oil pan. It just plugs onto a connecor on the rear face. Usually it's covered with lots of oily dirt and you will not see it.

Do not confuse this with the three wires going to the neutral safey/back-up lamp switch which is near by.

Look for the equipment decal usually fastened to the underside of the hood. This decal often falls off and get lost. Mine specifies H D 904 Auto Trans. Next line... Lockup torque converter. However it does not specify "electronic" anywhere.
There is a relay mounted near the left hood hinge for the electronic lockup converter. However there are several devices mounted next to each other to get you confused.

Be aware that the truck transmission tail shaft is longer than the one on the car. I don't know if you can swap on a car tail shaft to a truck transmission. Perhaps someone else here will know.

I will be watching this thread closely as I have long wanted a better gear spread from my Dart. I have heard rumors about this trans being less reliable than the 904 with a higher output application and this is why I have held off. Anyone want to chime in with a review?

Walter! Wow. Havent seen you in awhile. Something about a keyswitch---did you ever get that sorted?

Welcome back.

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

Whats the point in a lockup? I remember i was with my grandpa once driving up the mountain when suddenly the truck started shaking real bad, and it turned out to be the lockup...someone said to apply the brakes just so that the brake lights turned on to by pass the lock up. True? False?

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Drive it like its stolen, and be glad im not YOUR son...

The lock-up torque converter is a clutch inside the converter. Once it locks up, it is like a manual transmission with a clutch. You get rid of the slippage that normally occurs in the torque converter.

GM and other brands have it so if you apply the brakes the torque converter clutch unlocks. None of the lockup transmissions for the slant six have that feature.

I purchased an ignition switch on ebay that had the extra metal that fits in the slot on the instrument panel and keeps the entire switch from turning when you turn the key.

Just like the original 1963 Mopar version!

Back on topic...

I'm convinced, now, that the electronic lockup is the way to go. I just need to find a 1986 or 1987 Ram or van transmission.

I wonder if that tranny contains the additional clutch paks for heavy duty use?

--Walt Jackson
1963 Dodge Dart GT convertible.

Having automatic control of the lock-up via the ESA computer would be a lot nicer rather than having to flip a switch on and off all the time. There may be a way to rig up a control for it similar to what has been used for the automatic overdrive transmissions that are popular conversions these days.

Yes, the tranny has an extra clutch plate in each clutch and a double wrap kickdown band according to my '87 truck service manual.

Look for that transmission in pickup trucks too. Also be aware that the truck/van transmissions have a longer tailshaft than a car transmission. Does anyone know if we can swap the short tailshaft and housing from a car onto this "truck" transmission??????

Ya sure? My recollection is that this "unlock with brake application" feature is present in the electrically-operated torque converters for the couple years they were available behind Slant-6s, and that even the fully hydraulic ones have a similar feature controlled by the throttle pressure system—the torque converter unlocks in response to a sudden drop in throttle pressure.

Unlocking the torque converter with brake application is pretty necessary to avoid objectionable drivetrain shudder/shock...that doesn't necessarily mean all cars with locking torque converters do so.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Yes, I'm sure. My '87 Dodge truck 225 slant 6 has no connection from the brake pedal or brake wiring to the ESA computer (which controls the lock-up torque converter).

It uses several inputs to the ESA computer to unlock the converter. One is the curb idle ground switch on the carburetor. It unlocks the converter anytime the carburetor is at curb idle including deceleration from speed. I have also noticed that the converter in my truck will unlock when the manifold vacuum rises above a certain point (not sure what that point is) AND the road speed is below 55 MPH.
The ESA computer monitors several inputs to lock and unlock the converter between 36 and 55 MPH. Above 55 MPH the only thing that causes mine to unlock is when the carburetor is at full closed throttle making the curb idle ground switch sense closed throttle. Below 36 MPH the converter never locks up.

My experience with the full hydraulic lockups that once it locks up , it STAYS locked up until your road speed drops below a certain speed. I think that speed is just below the lockup speed.

I've got a car and truck transmission side by side on my basement floor and they are the exact same lenght. The car transmission is a lockup 78 aspen and the truck is from an 83 short bed ram. I think lenght differences are between 904 and 727 which are sometimes used in heavy slant six trucks.

So, as far as I know, nothing needs done to the tailshaft and it should fit the same. The truck transmission is supposed to have an extra clutch pack and a lower first gear. We'll see how it goes, because I'll be dropping the motor/trans in this weekend and testing it for next weeks race at North Wilks.

I've been told to stay away from the lockup converter for racing. The advice I was given was to swap in the front shaft, front pump, and converter from a non-lockup trans. I do not have the time or experience to do this procedure yet.

I would like to find a way to temporarily disable the hydrolic lockup feature. I would expect there is a spring or a port which can be changed in the valve body to disable the lockup. Anybody know? I'm posting a new topic so the question doesn't blow this one off track.

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1980 Aspen 225 super six

There was no special first-gear ratio in trucks. The wide-ratio A904 gearset came along in 1980 or '81, in cars and trucks.

Standard ratios are: 2.54 first, 1.45 second, 1.00 third
Wide ratios are: 2.74 first, 1.54 second, 1.00 third

The wide-ratio gearset is noisier and weaker.

I would like to find a way to temporarily disable the hydrolic lockup feature.[/quote]

You can disable the hydraulic lockup the same way you disable the accumulator for firmer shifts: Drop the pan, remove the lockup spring, and replace it with a spacer that holds the lockup piston in place and doesn't let it move.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

O.K. I will admit that I was wrong on that, I though the older trucks even prior to 1980 had the wide ratio, Thanks for the clearification, I learn something new every day. Glad I don't have to buy the wrong thing to learn my lesson. Thanks Dan.
Yes, but it's difficult to find a slant six in a car after 1980. They usually had a 318, although I've been told the guts of the transmission will swap into an older slant 6 case.
Great, more noise.

If it will hold up to a 318, I think it will be strong enough for my nearly stock super six.

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1980 Aspen 225 super six

Some of the guts will; there's no room in most \6 trans cases for the double-wrap band.
Oh, doubtless, if it starts out in good condition.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.