GyroMatic issues

[Marty C]

I’ve been driving my 52 Dodge for at least 2&1/2 years now and I have one issue with the transmission. Before I tell you the problem, I know the GyroMatic needs the engine speed to be as low as possible for proper shifting. 
The up shifts occur flawlessly at any speed when I take my foot off the accelerator as designed. The issue I’m having is that after a few miles when the engine is at operating temperature, the transmission has trouble downshifting back into the lower gear ( 3rd in drive range) . Sometimes it does downshift when i gradually come to a stop, BUT if you come to a regular stop in todays driving world, the engine will still be in high (or 4th in drive range)when you accelerate and in a few seconds of lugging, it will downshift with an audible clunk and a jerk into 3rd!

the only way to avoid this situation is the depress the clutch when coming to a stop. 
when the clutch is released it will be in the correct 3rd or low gear for acceleration. 
I would like to correct this issue. I had this problem last year, I removed and cleaned and lubricated the governor but it didn’t correct the issue. 
Any idea what could be wrong?

[Roofus]

Do you know this?

 

[Roofus]

What I would do, connect a bulb to the solenoide with threads long enough to enter the cabin by the passenger side hatch and see if there is a concordance between the lighting of the bulb and the gear passage 3/4 4/3, you will thus know if the problem is electric or hydraulic

[Marty C]

Damn I rewired all the solenoids and governor before I installed the carpet!

now I have no

access to the transmission inspection cover!

Thank you, I cannot believe how complicated this tranny is for 1950’s technology!!

Because the wiring and resistor pack is new, I’m guessing it may be that loose screw they talked about under that pipe plug

 

[Doug&Deb]

Marty, check the Imperial club website. They have a troubleshooting manual available for download. I had the same problem with mine and it ended up being bad wiring. 

[Marty C]

Hi Doug 

im positive the wiring is good 

it’s a brand new wiring harness , resistor pack thingy that mounts to carb and all new switches on carbs. 
If anything that has not been changed are the solenoids and governors 

there was an interruptor switch that was missing that I replaced with a new one from eBay 

I think you gave me the carb solenoid if my memory serves me!!😀

 

 

[Tom Skinner]

Marty C,

In the back of your Carb where the yellow wire goes is a switch with a piston inside. If it hangs up because of dirt affecting its operation you will have this problem.

I believe its called the kickdown switch right inside the carb. Dis -assemble the carb clean out the cylinder and the bake light/plastic piston and re-install.

That should correct it. another thing. sometimes the kickdown switch on the Tranny will hang up, you can remove the 30 Amp fuse from the Transmission Seleniod and re-install it I hope this is the solution I had similar problem and put a new kickdown on my Tranny and didn't need to because it was the Carburetor not responding to the Tranny Switch, because it was clogged up. Install a Gas filter to prevent future gunk ups.

There is a long trouble shooting process in the Service Manual to run down the actual problem but dollars to donuts you probably have a gunked up Carb Kickdown piston

Tom

[Roofus]

Quote

when you accelerate and in a few seconds of lugging, it will downshift with an audible clunk and a jerk into 3rd!

This is the normal functioning of kickdown if you drive at under 35 mph

I think it's your perception that is distorted, in fact your transmission works rather normally, variations may come from an inappropriate oil sensitive to heat ...

Edited Sunday at 07:51 AM by Roofus

[Marty C]

Hi Doug 

im positive the wiring is good 

it’s a brand new wiring harness , resistor pack thingy that mounts to carb and all new switches on carbs. 
If anything that has not been changed are the solenoids and governors 

there was an interruptor switch that was missing that I replaced with a new one from eBay 

I think you gave me the carb solenoid if my memory serves me!!😀

 

 

[Marty C]

Tom and Rufus 

I just want to clarify 

both of you are hinting it’s the kick down switch, but I’m not really kicking it down to go into a passing gear !

it’s normal stop and go traffic that’s when I’m slowing down to a light or stop sign , once stopped, it’s still in 4th. When I start accelerating it goes a few feet then clunks into 3rd!

it doesn’t shift into third by itself!

NOTE it works properly for the first few miles of driving 

Once the transmission gets warmer is when this happens so it’s temperature related adding to my confusion

[Roofus]

What oil is in the transmission?

[Tom Skinner]

Marty C,

Precisely, Marty, your tiny piston finally unsticks and drops down in your Carburetor Kickdown. Like your Manual says When you upshift everything is up, when you downshift everything is down. Try to see instead of replacing everything (Which is now big bucks) on your Transmission, Take your Carburetor apart and free up that small Kickdown Piston. The Transmission will only do what the Carburetor tells it to. Or do not, its your car drive it the way you like to. We are talking less than an hours maintenance work here. 

Tom

[Tom Skinner]

Marty, 

It will mess up the passing gear change as well. By the way I looked at your cover sheet. I played a Trumpet in High School and like Herb Albert etc. also.

Dude the small amount of labor to fix that Carb Piston will save you tons of money. I spent $250 for a Kickdown Switch on my Tranny (That I didn't need) only to correct the Passing/Kickdown Piston in the rear bottom of my Carb. I may sell it on e bay, My Tranny is a '48 M5 with the single Pole Kickdown Switch which is rarer than the M6 double Pole Switch. I'll be rich someday. LOL - Not

Tom

[Harley PHD]

have you looked at this old service reference book?

TROUBLE-SHOOTING IN THE HYDRACLICALLY OPERATED TRANSMISSION

a link to the IMPERIAL WEB PAGES

Transmission and Clutch Repair Information for Imperials and Chrysler Imperials

[Doug&Deb]

Marty, did you say you can come to a stop before it’s down shifting then when you pull away it down shifts? Doesn’t it stall? Mine didn’t down shift at a stop before I rewired it but it would always stall. I’m not sure if cleaning the breaker points on the governor cover would help or not. You may have already done that.

[Marty C]

On 3/2/2025 at 2:29 AM, Roofus said:

This is the normal functioning of kickdown if you drive at under 35 mph

I think it's your perception that is distorted, in fact your transmission works rather normally, variations may come from an inappropriate oil sensitive to heat ...

I know exactly how it’s supposed to work. The kickdown switch is supposed to kick the transmission from 4 to 34 added power while driving.. this has nothing to do with the issue. I am having.

The transmission is supposed to automatically downshift to the low (3rd gear) before coming to a stop at a light!

My transmission usually stays in high (4th gear) when I try to accelerate after the light turns green. In another words it doesn’t downshift!

This has nothing to do with the lockdown switch !!

Edited Monday at 11:45 PM by Marty C
Re wrote down shift to kick down

[Marty C]

On 3/2/2025 at 12:35 PM, Roofus said:

What oil is in the transmission?

Hydraulic oil 

[Marty C]

On 3/2/2025 at 1:35 PM, Tom Skinner said:

Marty, 

It will mess up the passing gear change as well. By the way I looked at your cover sheet. I played a Trumpet in High School and like Herb Albert etc. also.

Dude the small amount of labor to fix that Carb Piston will save you tons of money. I spent $250 for a Kickdown Switch on my Tranny (That I didn't need) only to correct the Passing/Kickdown Piston in the rear bottom of my Carb. I may sell it on e bay, My Tranny is a '48 M5 with the single Pole Kickdown Switch which is rarer than the M6 double Pole Switch. I'll be rich someday. LOL - Not

Tom

Hi Tom the only switch on the carb that has a plunger in it is the dashpot solenoid. I think this is what you and Rufus are talking about. 
the kick-down switch is only contacted when you floor it!

Not at all my problem. I think I only floored the gas once or twice in its life!!

it’s an old girl and I don’t push her

[Marty C]

Just now, Marty C said:

Hi Tom the only switch on the carb that has a plunger in it is the dashpot solenoid. I think this is what you and Rufus are talking about. 
the kick-down switch is only contacted when you floor it!

Not at all my problem. I think I only floored the gas once or twice in its life!!

it’s an old girl and I don’t push her

I play drums mostly to Herb Alpert and the Tijuana Brass but I love the sound of trumpets 

I’m going to see Herb and his new band Tijuana Brass and Other Delights at Lincoln center in March on his 90th birthday on the 31st🎺🥁

[Tom Skinner]

Marty,

Between the Kickdown Fixed Terminal and the Kickdown Switch Plunger words on your diagram above is the vertical Piston Housing that holds the piston I am talking about .

Not The Accelerator Plunger, not the Dash Pot Plunger. Just below the words Main Body to the right moving down you can clearly see where the Fast Idle Rod words are just below is a cavity holding that piston. This has a Spring that controls your Kickdown at your Transmission, and my friend if it hangs up because of carbon or dirt you will definitely have the exact problem you are describing to us. There is about 100 parts to this Carb. Get it off the Manifold Take out the Lower housing screws and remove the plunger and switch on either side of it and (If its stuck use penetrating oil to remove it and clean out the cavity and piston and reinstall the gaskets) Make your own gaskets if cost is an issue. Dude you can do this trust me its above the Spacer Gasket words arrow there is a piston in there that doesn't show up on the Rebuild Kit exploded Views.

It will take an hour and cost nothing, trust me. Take lots of pictures going in if you are not confident in yourself. You can do this, in order to become a Chrysler Guru!

Tom 

[Harley PHD]

Could he unplug the kickdown connector and tape it up just to test?  I've installed new wiring harness on new vehicles, and they were defective.  Pins in wrong connectors.  Could be a bad resistor or circuit breaker that fails when hot.

[Roofus]

Quote

Hydraulic oil

The Prestomatic transmission requires exclusively the SAE 10, the same as in the engine in cold weather, it is so important that it is written on the housing, if you have put oil intended for couples, I think you expose yourself to a few inconvenience.

Edited Tuesday at 07:49 AM by Roofus

[Tom Skinner]

Marty,

In The 1941 - 1948 Chrysler Service Manual, Page 143, there is a Cut Away Carburetor Picture of the Kickdown Piston inside your Carb that isn't sending the message to kickdown your Transmission at your Governor. It is either clogged or your Points on your Governor are, or something is amiss with your wiring. The Carburetor Solution I am suggesting costs nothing but a gasket and an hours work. You do not even need to open the Top of the Carburetor (Air Horn) to Service the part I am suggesting.

I was checking, testing, replacing parts, cleaning Governor Points etc., etc. until I did what I am suggesting to you my problem (Identical to yours) persisted.

I even had previously replaced my entire Engine Wiring Harness. I spent close to a thousand Dollars to sort out my problem - namely a clogged Kick Down Piston in my Carburetor. Good Luck with your solution. Please post us what you did to find yours, I typically don't post a lot on here anymore so consider yourself lucky to get this information because sorting out my Transmission Glitch was a MFSOB to put it lightly. Also change your 30 Amp. Fuse at your Transmission Solenoid.

Best of Luck to you. (The Wire from that Part of the Carb to the Governor is Yellow)

Tom

[Marty C]

On 3/3/2025 at 9:02 PM, Tom Skinner said:

Marty,

Between the Kickdown Fixed Terminal and the Kickdown Switch Plunger words on your diagram above is the vertical Piston Housing that holds the piston I am talking about .

Not The Accelerator Plunger, not the Dash Pot Plunger. Just below the words Main Body to the right moving down you can clearly see where the Fast Idle Rod words are just below is a cavity holding that piston. This has a Spring that controls your Kickdown at your Transmission, and my friend if it hangs up because of carbon or dirt you will definitely have the exact problem you are describing to us. There is about 100 parts to this Carb. Get it off the Manifold Take out the Lower housing screws and remove the plunger and switch on either side of it and (If its stuck use penetrating oil to remove it and clean out the cavity and piston and reinstall the gaskets) Make your own gaskets if cost is an issue. Dude you can do this trust me its above the Spacer Gasket words arrow there is a piston in there that doesn't show up on the Rebuild Kit exploded Views.

It will take an hour and cost nothing, trust me. Take lots of pictures going in if you are not confident in yourself. You can do this, in order to become a Chrysler Guru!

Tom 

Tom I’m definitely going to pull the carb and make sure that plunger is clean!!!

thank you so much for all your help!

I’ll keep you posted on my progress!

On 3/3/2025 at 9:02 PM, Tom Skinner said:

Marty,

Between the Kickdown Fixed Terminal and the Kickdown Switch Plunger words on your diagram above is the vertical Piston Housing that holds the piston I am talking about .

Not The Accelerator Plunger, not the Dash Pot Plunger. Just below the words Main Body to the right moving down you can clearly see where the Fast Idle Rod words are just below is a cavity holding that piston. This has a Spring that controls your Kickdown at your Transmission, and my friend if it hangs up because of carbon or dirt you will definitely have the exact problem you are describing to us. There is about 100 parts to this Carb. Get it off the Manifold Take out the Lower housing screws and remove the plunger and switch on either side of it and (If its stuck use penetrating oil to remove it and clean out the cavity and piston and reinstall the gaskets) Make your own gaskets if cost is an issue. Dude you can do this trust me its above the Spacer Gasket words arrow there is a piston in there that doesn't show up on the Rebuild Kit exploded Views.

It will take an hour and cost nothing, trust me. Take lots of pictures going in if you are not confident in yourself. You can do this, in order to become a Chrysler Guru!

Tom 

 

1 hour ago, Tom Skinner said:

Marty,

In The 1941 - 1948 Chrysler Service Manual, Page 143, there is a Cut Away Carburetor Picture of the Kickdown Piston inside your Carb that isn't sending the message to kickdown your Transmission at your Governor. It is either clogged or your Points on your Governor are, or something is amiss with your wiring. The Carburetor Solution I am suggesting costs nothing but a gasket and an hours work. You do not even need to open the Top of the Carburetor (Air Horn) to Service the part I am suggesting.

I was checking, testing, replacing parts, cleaning Governor Points etc., etc. until I did what I am suggesting to you my problem (Identical to yours) persisted.

I even had previously replaced my entire Engine Wiring Harness. I spent close to a thousand Dollars to sort out my problem - namely a clogged Kick Down Piston in my Carburetor. Good Luck with your solution. Please post us what you did to find yours, I typically don't post a lot on here anymore so consider yourself lucky to get this information because sorting out my Transmission Glitch was a MFSOB to put it lightly. Also change your 30 Amp. Fuse at your Transmission Solenoid.

Best of Luck to you. (The Wire from that Part of the Carb to the Governor is Yellow)

Tom