C38 Chrysler 1948 Windsor Transmission Issue

[Erwin Petersen]

Our C38 Windsor (in The Netherlands) currently has the problem that the Transmission does not shift in both low (1/2) and high gear (3/4). The manual lever at the steering wheel operates normally. The Fluid Drive and Transmission were not topped with oil for ages and operated nicely until recently (with the subtle clank-sound during the shifting). Could the cause be a lack of fluid? Any other possible cause imaginable?  

Edited August 31, 2022 by Erwin Petersen (see edit history)

[Rusty_OToole]

It could be low on oil. The transmission is filled separate from the Fluid Drive unit. The transmission will not shift if it is low on oil.

 

Could also be a loose or frayed wire somewhere. Check the wires from the transmission to the carburetor, and from the carburetor to the ignition coil.

 

It is possible the contact points in the governor are dirty. If that happens the trans will not shift down when you stop the car. You can take the top off the governor and clean the points. Be careful, they are made of silver and are not as hard as ignition points or relay points. Use contact cleaner spray, or  brake cleaner spray to remove grease and drag a strip of white typing paper between the points until it comes out clean.

 

If the idle speed is too high the trans will not shift. Idle speed should be very low, 400 RPM, about half the speed of a modern car.

 

Those are the most common causes of not shifting.

Edited August 29, 2022 by Rusty_OToole (see edit history)

[Erwin Petersen]

Thank you for your response. That helps. The system does not shift up. It stays in 1 during low gear and in 3 during high gear. I limited the max continuous driving speed (with high relatively high rpm) to 30 - 35 mph. We will check the items you mentioned. Thx. I will use ISO 32 TDH-oil for topping up the Fluid Drive and Transmission. This seems to be correct based on the info of this forum.

[Rusty_OToole]

I would check and top up the transmission first. Trans oil should be changed every 10000 miles.

There are a couple of long threads in the Chrysler section dating back to 2008 that cover these transmissions in depth. Worth searching for if you are new to these models.

[keithb7]

You may have the vaccu-matic shift system. The M5 transmission.The next variation, the the M6, if you have it, I go through some it if here:

 

 

 

 

I was learning as I go. Reading, studying and then taking things apart in the shop. I make some slips-ups here,  but the basics and understanding is here.

Shifting happens with a sealed cylinder building oil pressure, forcing a piston to move. Piston is connected to a shift fork.  When you slow a switch engages in the tranny,

releasing oil pressure. Spring pressure overcomes oil pressure and the piston goes back the the other direction down shifting. 

 

Lots of things going on in the shifting system. Ground speed, throttle position. A spinning governor switch, 6V large solenoid.

 

Start with the easy stuff . Make sure you have the proper weight of oil. Check voltage when and when it is supposed to be present at various spots in the car. If you require precise instructions I have them, that I can send you. Send me a personal message if wanted.

Ensure  the engine idle speed is set to spec. If idle it too high transmission will delay shift, or not shift at all.

 

The oil pump turns off the drive shaft, so it builds oil pressure when moving. You need oil pressure, you need a return spring that works, An oil port that is clear and opens when needed. A check ball and a spring that works.

 

Keith

 

Here is the governor switch and solenoid system explained:

 

 

Edited August 29, 2022 by keithb7 (see edit history)

[Akstraw]

This sounds like an electrical/solenoid issue to me, not a fluid issue.  That’s where I would look first, though keeping all fluids full to spec is important for smooth operation in any car.

[61polara]

6 hours ago, keithb7 said:

You may have the vaccu-matic shift system.

Vacu-matic was pre-war only Chrysler and DeSoto.  Keithb7's info is great.

[Rusty_OToole]

Trans won't shift if the oil is too low or if idle is too high. If the wiring is messed up it will still shift but  not kick down. If the governor is dirty will not shift down when you come to a stop.

 

They are a simple, rugged transmission once you get to know them. Much easier and cheaper to fix than a Hydramatic or other early automatic.

[Erwin Petersen]

Thanks for the help and suggestions.  Wiring diagram C38 shows kickdown solenoid electrical connection. But is the normal shifting of the transmission a purely mechanical one?  

[Rusty_OToole]

The transmission is shifted by a built in hydraulic cylinder and pump. The cylinder slides the shifter fork. It is controlled by an electric valve connected to the carburetor. When you close the throttle it actuates the switch. This is the shift between low and high gear.

 

There is also a gearshift lever on the column that allows you to shift manually to reverse, low range or high range.

 

Maybe this diagram will help explain things.  Study it for a while and many things become clear.

 

[keithb7]

There are many things going on here to make this semi-auto work. They are all simple by design yet to get your brain wrapped around all of it can be challenging.  Simple, yet genius really. 
 

I like how the freewheeling control sleeve (lock ring) moves forward with the direct speed drive clutch. You get dynamic braking on hills in low range only. Assisting on down hill slopes. Yet in high range it free wheels.  
 

Its basically a 2 speed with hi/low range. Passing gear (sort of like 3rd) is skipped when you start in low, then allow auto shift to second. Then you manually shift column lever into hi-range. Going into sort of like 4th gear.  The one and only way to get into what you may think is 3rd (passing gear) is when you are in high range (4th sort of) under 30 mph or so. You mash the foot throttle.  This activates a linkage switch on the  Carb. The ignition coil is temporarily sent to ground, killing all spark to all plugs. This briefly takes the load off the tranny input pinion allowing a shift to happen. As soon as your let off the gas again, it shifts back to 4th. 
 

I made this video when I first owned my 53 Chrysler. At that time I thought the car could up shift through all 4 tranny gears. That’s incorrect.  It goes; bull low, then auto shift to 2nd, then manual shit to 4th. Sorta. Lol. It’s quite the system. 
 

https://youtu.be/z4L0NURxm64

[Erwin Petersen]

Great diagram Rusty_Otoole. Helps a lot. The "arrows" at the carburator, governer, anti stall control and interuptor-switch are ground-connections? My problem seems to be more a transmission problem than a fluid drive problem. Coming friday on the bridge to trouble-shoot with the tips/tricks you all gave. Thx.

[marcapra]

https://mymopar.com/mtsc-1948-volume-a1-checking-the-hydraulically-operated-transmission/

[Erwin Petersen]

Thx, great instructive video.

[Erwin Petersen]

Gents. It seems the kick down relais is not functioning. Transmission oil change and fill-up did not solve the problem. Electrical tests revealed the kick down relais as the cause of the problem. Where can I get hold of a “new” kick down relais?

[Rusty_OToole]

For a relay you might try Chrysler parts specialist Andy Bernbaum or check Ebay.

[c49er]

The Autolite M-5 transmission relay points can be easily cleaned up...most likely problem if there is a relay issue.

The relay fuse holder and contact sufaces can get corroded and will cause imediate upshifts but no down shifting until coming to a complete stop with the clutch pushed in.

......not your issue though.

You might want to Open up the relay box and carefully check the two sets of points inside...clean them up carefully with a fine points contact file and contact cleaner if they look smoked or burnt.

A new correct Autolite five terminal relay can be difficult to find.

[Erwin Petersen]

Drove the car yesterday and the problem initially seemed over but later reoccurred intermittently. Very frustrating. 

[timecapsule]

I have the same car.    So did you solve the relay problem?  Sometimes it's the simple things.  Like maybe the contacts on that fuse that is mounted on the relay needs cleaning.  I'm sure it was already mentioned previously about how the carburetor must idle at about 450 rpm's or it won't shift properly. 

Did you do something to solve the problem since your original posting?  

Judging by what you just said about the issue reaccusing intermittently.  I'm wondering if it could be a frayed wire somewhere.  Those original cloth sheathed wires get pretty brittle over the decades especially in the engine compartment area.  I know how difficult it is to trace them individually especially around the steering column area, below that transmission relay.  Sometimes it's difficult to identify the colour of the tracer on each wire, because it gets so faded over time.  Eventually I cut open the bundle of wires there and that showed nice brightly coloured wiring with clear colour tracers quite visible.  Then after I identified all the wires I rebounded them all with new electrical tape.   It just takes lots of time and "careful" patience to do a continuity check on each wire and record each wire and label it as you track it down as to where it came from and where it goes.  Basically making your own wiring diagram.  That process also helps to understand what does what and when certain things happen to make the car go down the road smoothly.  

You may have already done all this the first time around.  But since it is happening intermittently now.  Perhaps the wires need to be checked again. 

Have you tried posting your problem over on P15-D24?  Great bunch of really knowledgeable guys over there too.

[Erwin Petersen]

Thx Timecapsule. What you write is excatly what we plan to do. I also believe the problem should be somewhere in the wiring. That is the next step we will take: making our own wiring diagram as you say. Thanks for your reply. I will post our results in this forum.

[Erwin Petersen]

Dear Forum Chrysler fans. Today we solved the transmission issue. The root cause of the problem turned out to be a wiring ground on/in the housing of the Governor. Thanks to all advice and useful suggestions. We learned a lot about the system and are ready for the next cardrive. Thanks all. Erwin Petersen - The Netherlands. 

[Rusty_OToole]

It's usually some simple little thing, the hard job is finding it. Hope you and your family have some nice long drives with your big comfortable Chrysler.

[Erwin Petersen]

Thx Rusty_OToole: it is certainly a comfortable car. And still going strong after 75 years in our family. Never sold in 75 years. 

[auperle]

On 8/31/2022 at 10:24 AM, Erwin Petersen said:

Great diagram Rusty_Otoole. Helps a lot. The "arrows" at the carburator, governer, anti stall control and interuptor-switch are ground-connections? My problem seems to be more a transmission problem than a fluid drive problem. Coming friday on the bridge to trouble-shoot with the tips/tricks you all gave. Thx.

Hallo Erwin , kan ik met jou in contact komen? Ik heb het zelfde probleem maar ik kom er niet uit..

[Erwin Petersen]

Geen probleem: 06-51224610

[timecapsule]

On 9/6/2023 at 5:57 AM, Erwin Petersen said:

Thx Rusty_OToole: it is certainly a comfortable car. And still going strong after 75 years in our family. Never sold in 75 years. 

That's fantastic that your family has had the car all it's live.  My '48 Windsor still ranks at the top of my list of cars for enjoyment.  Even though I'm running bias ply tires the ride is really smooth on rough roads.  I'm constantly driving with a permanent smile on my face as I witness the fluid drive working flawlessly.  If I ever have a hard time falling asleep in bed, I'll grab a book and head off to the back seat of my Windsor.  I'm asleep in no time at all. 😉