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ShaneGTO

M6 (Gyro-Matic) stalling issue

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Hi guys, so I have a 1949 Dodge Coronet with the semi- auto transmission. When I start the car up, it goes into gear and takes off beautifully. But after I let it automatically upshift and then I come up to a stop, the car doesn’t downshift. But then when I go to accelerate again, the car cuts out and dies as if I just turned the key off. (No sputtering or anything). Sometimes when I try to take off after being I’d direct drive instead of stalling it will bog out and then kick back in and sometimes downshift and sometimes not. It seems like an electrical issue to me since it shuts the car off in a very uniform electrical way. I figure it has something to do with the interrupter switch or resistor but I am wondering if you guys have had this happen before. The carb is tuned properly and runs very well when driving down the road, in neutral, and taking off as long as I have not let it upshift yet.

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Do you have the proper Dodge shop manual? They have a good section on trouble shooting these transmission systems. Not downshifting could be electrical or hydraulic related.

 

Regarding your comment on the interrupter switch.

One of my shop manuals reads: Ignition Interrupter Resistor Check: With engine running ground the blue wire on the resistor, or at the interrupter switch. This should stall the engine. If the engine does not stall, either the blue wire from the interruptor switch to the resistor, the resistor itself, or the blue wire from the resistor to the coil is at fault.

 

My understanding is, when you floor the accelerator when in 4th, at certain speed,  the carb linkage sends a signal to the interruptor switch. It sends the ignition system coil to ground momentarily to remove engine power (load) from the transmission, to allow for a down-shift. There is also an anti-stall control on the carb. This is a dashpot  to control a slow closing of the throttle. It prevents stalling upon quick release of the throttle. 

 

It appears there are several  systems to check. A good Mopar manual is highly recommended. Several of the tests are simple, done with a continuity light.

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There are a bunch of Chrysler master tech videos on Youtube that might be of assistance.

Here is one but there are other training videos on the transmission issues.

 

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Thanks guys, I do have the motor manual which goes into pretty good detail. And after watching those master tech videos I’m thinking it may be something dealing with the governor not making the connection to release the pressure on the piston. I tried to remove the cap to the governor today but it wouldn’t budge. So tomorrow I’ll see if I can get it off the transmission and on the bench to try and baby the lid off and check/ clean the contacts

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There is a troubleshooting manual available for download on the Imperial website. I highly recommend this. There are easy ways to check the trans. I had the same problem and my solution was bad wiring. A trans harness is available if needed. 

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