A904 Lockup Converter Won't Unlock

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jhawk

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I just picked up a 69 Dart with a 340. Purple cam of some sort, headers, intake, etc. It is running an A904 with lockup converter that appears to be locked all the time. I've seen where you can use a ball bearing in the lockup valve to disable the lockup which I may do. Is there anything else I should look at first?

Thanks,
Jim
 
If the convertor clutch was truly lock-up all the time the car would stall when you can to a stop. Or stall as soon as you put it in gear.
 
jhawk said:
I just picked up a 69 Dart with a 340. Purple cam of some sort, headers, intake, etc. It is running an A904 with lockup converter that appears to be locked all the time. I've seen where you can use a ball bearing in the lockup valve to disable the lockup which I may do. Is there anything else I should look at first?

Thanks,
Jim
Click to expand...

Usually a converter that won’t unlock is caused by the hydraulic applied ring that presses the clutch disc inside is jammed.
Never seen one that was caused by an unwanted hydraulic application.
 
TrailBeast said:
Usually a converter that won’t unlock is caused by the hydraulic applied ring that presses the clutch disc inside is jammed.
Never seen one that was caused by an unwanted hydraulic application.
Click to expand...
Thanks man, can you expand on this I'm brand new to these transmissions? Are we talking about the clutch inside the converter and if so is there anything to do other then throw in a new converter?

Thanks,
Jim
 
jhawk said:
Thanks man, can you expand on this I'm brand new to these transmissions? Are we talking about the clutch inside the converter and if so is there anything to do other then throw in a new converter?

Thanks,
Jim
Click to expand...

The converter clutch is applied by trans fluid hydraulic pressure, and a piston shaped like a ring.
If that ring gets cocked sideways, or jams on debris it can stick in the applied position.
I have unstuck them by light/medium multiple taps on the converter around the circumference closest to flexplate edge.

That works sometimes and sometimes not.
Multiple on/off switching of the lockup function can also free them.
The only other thing I have seen work is to add a bottle of LubeGard.
This additive is highly regarded for its ability to free sticking valves in automatic transmissions.
It’s a friction modifier used in many trans shops, and can solve a variety of issues.

Sometimes the clutch material comes loose from it’s backing and stacks up jamming the clutch in the applied position.
There is no fixing this unless the converter is sent in for disassembly and repair.
 
Did anyone by chance use bolts on the flex plate that are too long?
 
TrailBeast, thanks for the info I'll try both tomorrow. Hellrats, no idea about flew plate bolts. I won't get a a chance to look under the car until tomorrow.

Jim
 
I was just saying about the bolts because it they are too long than can dimple the back of the convertor and cause problems. Hope you get it figured out quick and easy.
 
jhawk said:
TrailBeast, thanks for the info I'll try both tomorrow. Hellrats, no idea about flew plate bolts. I won't get a a chance to look under the car until tomorrow.

Jim
Click to expand...

Just so we are clear about symptoms, most convert clutches that are stuck will first be indicated by coming to a stop and it kills the motor like a stick that the clutch wasn’t pressed.
Then upon restart immediately kills the engine when put in gear just like dropping the clutch at idle.
 
That's exactly what is happening. I'll get under the car in a bit and see if the tapping the converter trick and Lubegard works.

Jim
 
After losing the brakes in the car, I finally got back to this. The transmission is an electronic lock-up transmission. I've read both 12v to the solenoid locks it, and 12v unlocks it. I put 12v to it today and didn't hear the solenoid activate. I'll dig into it more tomorrow. Any advice is appreciated.

Thanks,
Jim
 
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