Gyromatic

[Tams50]

50 Dodge Coronet 

Gyromatic shifts up and down as it should in low range from first to second and back without use of the clutch, but in high range seems to be stuck in 4th gear. I have drained and refilled the oil (10w) three times and engine rpm is 450 at idle. I have a manual, and vintage chrysler service videos . I rebuilt the motor and carb , wiring, cooling system. Any help appreciated before I pull the tranny.

Edited May 25, 2020 by Tams50
Shifting explained

[dpollo]

something strange because if the  one -two shift works in low range, the same gears are in use for three-four.

 

Maybe Dodge b4ya  will know

[keithb7]

That's an interesting scenario as the hydraulic shift that takes place is identical in either high or low range. I'll be following along to learn. 

The manual does a pretty good job laying everything out and offering troubleshooting steps. 

 

Have the spinning governor points been cleaned/inspected? They mention a damaged or defective speed blocker ring as a possible candidate. Saying this, the same parts seem to be functioning fine in low range.

 

Is it possible, that although idle is set properly, at higher speeds when the throttle is depressed further, when you lift your foot to initiate a shift something in the throttle linkage is binding up a little, not allowing the engine RPM to drop quickly? This slows down the engine and the tranny input pinion to allow for completion of speed synchronization. If the engine does not slow down, the tranny input pinion will not slow down,  the shift won't complete.

 

When driving in 4th, what happens when you are idling up to a stop sign and stop? I assume it does not drop into third? What about when you are cruising along in 4th, about 25 mph  and mash the gas pedal to the floor. Does it down shift into 3rd then?

Edited May 25, 2020 by keithb7

[DonaldSmith]

The whole idea of the Fluid Drive was to minimize and smooth out the clutching. For Fluid drive with a three-speed, take off in third gear. For the semi-automatic, start off in third, and let it upshift to fourth.  Idle at the traffic lights without having to use the clutch. 

 

I don't use the "power" range under normal driving circumstances.  If I have a steep slope, as from a field to a drive, or if I'm trying to get the car up some ramps, i  will start in first.  Otherwise, I'm in no hurry.   Ty driving third-to-fourth for a while, if you can stand the leisurely pace.   See if it upshifts and downshifts between the two gears like it should. 

 

(Dad was driving with Grampa once.  Grampa took off, shifted to second, and kept going. Dad suggested that he shift into third.  Grampa replied, "I'm going fast enough."

 

[Dodgeb4ya]

If the power range auto upshifts normally it should also auto upshift in the driving range.

So if you put the shift lever in the driving range stopped (down all the way) you are saying it is already in auto upshifted 4th gear at a complete dead stop?

I don't see how it could be in auto upshift 4th gear starting from a dead stop as there is no oil pressure created by the transmission oil pump at a stop?

The fact that it correctly shifts up and down in the power range generally means the wiring and blocker ring and sleeve are ok as long as there is no harsh/banging upshift or down shifting.

Have you driven off from a complete stop starting only in the normal driving range to see if it would upshift into 4th above say 20mph...?

Not starting in the power range then shifting into the driving range.

 

 

[greg g]

Could it be you are starting out in third and not upshifting?

[Tams50]

Thank you all. I appreciate all of response. I have driven in the high range and come to a stop without the clutch, the acceleration is poor to say the least with no upshift. After reading all response , could it be the dashpot adjustment ?  I know the ignition cuts off to allow the upshift but like mentioned shifting is perfect in low. We have a steep hill with a stop sign above our garage.

[Dodgeb4ya]

Clean the governor contact points..

They are silver...use contact cleaner.

If the solenoid is not energized oil pressure will remain at 40 lbs preventing a downshift at a stop.

The solenoid is energized via the governor points closing this creating the ground circuit for the downshift solenoid.

Though odd it downshifts in the power range but I think it's the points being oily...clean em up.

[Tams50]

I cleaned the points and checked the oil level ,it was overfilled because I only lifted one front side to have access. Shifts as it should now. I need to reset the magnetic dashpot to prevent stalling on abrupt stops. Thanks for the advice. Anyone with a gyromatic should watch the chrysler master tech video, it is far better than the manual.

 

[greg g]

The Imperial Club website has the tech film strip version for care and feeding of your m6 trans by what ever name they go by.

[Tams50]

I cleaned the points and checked the oil level ,it was overfilled because I only lifted one front side to have access. Shifts as it should now. I need to reset the magnetic dashpot to prevent stalling on abrupt stops. Thanks for the advice. Anyone with a gyromatic should watch the chrysler master tech video, it is far better than the manual.

 

[MarcDeSoto]

http://www.mymopar.com/index.php?pid=382  Trouble shooting the M-6 semi-automatic transmission.  1949-1952

 

 

 

http://www.mymopar.com/index.php?pid=632   Trouble shooting the M-5 semi-automatic transmission.  1946-1948