1951 New Yorker M-6 trans downshift issue

Hello.. I have a question about a 1951 Chrysler New Yorker Fluid Matic. I have gone thru the drive train and electrical system of the engine/tranny and verified the operation of the components. Everything seems to work fine and upshift with no problem, but when I come to a stop it seems as if the interrupter switch "holds" on just a shade too long and stalls the engine rather than "interrupt" the ignition. This happens about 85% of the time but it will always restart right away.

The only component that I know for sure is not working is the anti stall dashpot on the carb. But as I understand it this has to do with deceleration and not ignition cut out.

My question is: What should I check or look into that would be causing the "too long of an ignition interruption" situation causing the engine to stall? Dwell?, Timing?, Piston return spring in trans? Interrupter SW?

I appreciate all of the knowledge that is found on this forum and all of the helpful people.

Thank you

John

Here ya go. Watch this original MTSC trouble shooting training video on your M-6 Trans. There are 2 or 3 vids on the M-6 trans. Watch em all!

Bob

Thanks Bob! I have looking at all the MTSC literature and slide shows from the imperial site. The conclusion I have come to is that when the car is warm, the downshift from 4 to 3 happens way too late, when I'm literally just about stopped and of course engine is idling and of course just stalls out. I'm starting to lean towards gov points closing too late, instead of at about 10-11 mph. I had a chrysler guru and another chrysler guy tell me that ATF will work fine instead of 10w or ISO 32 due to its tolerance to heat... Maybe there is a viscosity issue and the fluid can't drain away from behind the piston fast enough.

Your thoughts, gentlemen?

Nevertheless, the owner of the car wants me to shift gears and work in his 63 riviera, so I guess the chrysler gets moved to the back burner for awhile.

If the oil in the trans was too thick, yes it could cause a delayed downshift. Your problem is that oil pressure is not getting completely dumped to zero when you hit 10-13 MPH when coming to a stop in high range gear-5-7MPH in low range.The stalling at idle? Does the engine run well and idle extremely smooth? It should. Even if the Anti-stll does not work normally the engine should not stall coming to a normal driving slowing stop. Possibly the interupter switch circuit is faulty in some way and killing ignition when the trans shift piston momentarily kills ingnition to release the blocker ring torque. The resistor could be damaged. To see if it will downshift at a normal 10-13 MPH when coming to a stop in the normal high range, connect a wire to the "yellow" governer downshift circuit say at the carb downshift switch. Run it into the car where at you will you can ground the other end of this wire by just touching it to a metal ground like on the steering coluum somewhere convenient. Now drive the car and come to a normal stop and at say at 10MPH ground the wire and hold it grounded as you com to a stop. It should downshift imediately as a normal stopping downshift should occur. If it does now downshift, it means that the wiring, resistor or governer are probably the problem- not oil viscosity. The two terminal interupter switch also needs to be tested by taking it off the trans and use a ohmmeter and see that without pushing the ball it should read open, or have NO continuity. Push the ball in and the meter should show a reading and continuity. The governer points could be oily and need a gentile cleaning with a cloth and cleaner-they are silver don't file them. Also the governer could be worn-that is the plunger phenolic resin shaft tip is worn down. Just remeber the solenoid needs 6 volt power to dump oil pressure to cause a down shift. It there is no voltage to the trans solenoid the trans will imediately upshift from a stop and stay in high direct at all times and will not downshift even at a complete stop unless you hold the clutch pedal down and wait 5-10 seconds at a full waiting stop for pressure to bleed off back to

I've posted a couple governer pics off a 1946-8 M-5 but are basically the same as the 1949-53 M-6 trans. Follow the Imperial site info and you will get it fixed.

I am having a similar problem and started a thread about it. John (paripam) did you ever figure out what the problem was ? Thanks, James

Erratic downshift can be caused by dirty points in the governor. A squirt of contact cleaner or brake clean spray will clean them up. Drag a strip of white paper between them to clean off any dirt. The points are soft silver so do not use a file or sandpaper.  Do this every 50 years and you should have no more trouble.