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M-6 Transmission Downshift Question


Guest CharlesinMaine

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Guest CharlesinMaine

I have a 1953 Chrysler T&C 6 cyl with a two range M-6 transmission. When in drive or high range in 4th or highest gear and come to a stop my transmission will not downshift into "third" unless at a dead stop and not all of the time. If I depress the safety pedal (clutch) it will down shift upon any stop at once. I have it tuned up, and its idle is about 375 rpm. Are ther any obvious attempts I can make to rectify this?

I also have a kick down plunger on my carb but no wires or evidence of where wires would hook up. Is there a special option for this switch option?

Thanks for your assistance,

Charles In Maine

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Charles,

The symptoms you describe usually indicate a failure in the electrical controls of the M6 transmission. Almost any failure in the electrical controls, including no supply voltage from the circuit breaker, will prevent the transmission from properly downshifting at low road speeds. About the only non-electrical problem that can cause failure to downshift at low speeds is a stuck ball valve, the one that is operated by the solenoid.

The hydraulically operated transmission will downshift at a stop, with the clutch depressed, even if the electrical controls don't work. This happens because, with the car stopped, there is no hydraulic pressure to maintain the upshift hydraulic piston and, with the clutch disengaged, no torque load on the gears to prevent a downshift.

The Chrysler Service Guide "Troubleshooting in the Hydraulically Operated Transmission" should be helpful in tracking down your particular problem. It's available on the Imperial Club website at

http://imperialclub.com/Repair/Lit/Master/024/index.htm

There's a good schematic of the transmission and its electrical controls here:

http://imperialclub.com/Yr/1953/fsm/Page570-r.htm

Doug

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Your shifting problem may be related to the carb control wire. All I can suggest is to get a repair manual and figure out where the wire is supposed to go. Your car is supposed to have a Carter carburetor, model BB, number E9A1, E9C or E9C1. If the carb has been replaced at some time that might explain the missing wiring.

There should be a kick down switch at the rear of the carb. This has a straight wire connector that plugs into a brass tube. The brass tube has a slot where a little wire retainer clip goes in to hold the wire. If the clip falls off there will be nothing to stop the wire falling out. Look for a little brass tube about 1/8" dia with a slot in it, at the back of the carb, pointing toward the left.

There should also be a switch at the front top of the carb with 2 wires that push into 2 brass tubes or loops.

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Guest De Soto Frank

Charles,

It sounds like the problem is either in the wiring, the governor, or the interrupter circuit.

For the tranny to downshift, two things have to happen:

1) Oil pressure behind the shifting piston has to be relieved ( Solenoid is energized either by the governor points closing or by the kick-down switch on the carb being activated)

2) strain on gears has to be relieved ( interrupter switch closes, momentarily shorting the ignition ( fraction of a second), to allow one of the internal springs to move the direct-speed sleeve back to "low".

If the tranny won't downshift except when at a full-stop suggests that the solenoid is not operating, and therfore not relieving the pressure behind the shifting piston.

Would suggest getting out your shop-manual and following the trouble-shooting process and determining that the solenoid, govnernor, interrupter-switch, and wiring are all in good order.

Good luck !

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