Fluid drive will not shift to higher gear.

[jharring10]

I recently rebuilt my entire fuel system on my 49 DeSoto first series due to ethanol causing it to hesitate badly. New gas tank w gas gauge sensor, rebuilt carb and when I removed the rubber fuel line I found the issue as there wasn’t much left of the line and was sure sucking air. Replaced the line and the sucker fired right up! Little did I know that the fuel pump was leaking like a sieve.  Ethanol apparently destroyed the seals. Bought a 6 Volt electric fuel pump with an attached fuel filter and problem solved. She now starts and runs as good as ever but now a new problem and that is Fluid Drive. When I took the car out for a test drive, she backed out of the garage in reverse no problem. I then put her in high gear (shifter down) and she took off but will not shift into the second gear. I have been taking her in the neighborhood for the past couple of weeks trying to loosen it up but no luck.  Semi-Automatic  transmission issues have been my biggest fear with this car and now it has happened. I have never done anything to this tranny. When I spoke with some of the older mechanics about fluid drive, their response was “if it isn't broke don’t fix it”.  It was recommended that I start with changing the fluids on both the tranny so I recently drained the tranny and added fresh 10w oil. It was also recommended that I disconnect the solenoid on the tranny to see if she is forced in the higher gear so I did. There are three connection but I think I removed the right one (see pic). By the way I pulled apart and cleaned the contacts as recommended in another forum. I took her for a ride and she was in fact now in the higher gear. I then decided to go for a little a cruise on a main road as she may be a little slow taking off but I can now run at an acceptable cruising speed. I got a little way up the road and she stalled and I could not get her started. I reconnected transmission solenoid  and she started right up but ran in the lower gear. Disconnected again and same results. Not sure what correlation the transmission solenoid has to do with providing fuel to the carburetor.  Could the electric fuel pump have anything to do with the issue . Any help would be greatly appreciated.

[Plymouthy Adams]

has the baseline rpm been altered that would cause it not to drop to the point needed to allow shifting

[Niel Hoback]

Ditto. Idle speed too high.

[Dodgeb4ya]

Save some time and just the fuse on the fender relay and see if it will up shift.

You don't need to disconnect the solenoid wire.

With out electrical power to the trans it will immediately up shift if the internals are working.

It will be veryyyy slow to downshift with out the fuse installed when coming to a stop with the clutch pushed in.

This all is for up shift testing only.

[jharring10]

I have decreased the idle as low as I could without the vehicle stalling then took it for a ride. No change. Still would not shift. Dodgeb4ya, You said to "Save some time and just the fuse on the fender relay and see if it will up shift". Are you saying to remove the fuse on the fender relay and see if it will up shift?

[jharring10]

Found the fuse. I was hoping that is was blown but it is not. I'll try to take it for another spin tonight with the fuse removed. 

[greg g]

http://www.imperialclub.com/Repair/Lit/Master/012B/index.htm

 

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

[jharring10]

I pulled the fuse per the recommendation of Dodgeb4ya and she up-shifted perfectly. Down-shifting was slow as described. Put the fuse back in and will not up-shift again. What does this indicate?

[mopar_earl]

Believe you have some wiring connection issues. Triple check all your wiring per the print in your manual. The solenoid is controlled by the governor. So either the wiring circuitry is wrong bypassing the governor or the governor isn't opening the points to open the circuit to the solenoid.

Earl

[dpollo]

 It is very likely the wires on the carburetor have been reversed.

 

The electrical control is for kick down and it dumps the hydraulic pressure . so if the circuit is energized all the time the trans cannot upshift since pressure is not built up.

[DonaldSmith]

From someone who has reversed the wires on the carburetor:

 

Red (or formerly red) wire from "SOL" post on the trans relay to "Carburetor Anti-Stall"  on the top front of the carburetor.  This wire branches off to the Solenoid.  

 

Yellow (somewhat) wire from the "TH" post of the relay to the "Kick Down Switch"  at the side of the carb facing the engine.  This wire also branches off to the Governor Switch. 

 

Black (maybe faded) wire from the "INT" post of the relay to the Interrupter Switch. 

 

In the photo posted above, the solenoid is circled.  The bottom of the photo is at the back of the floor opening.  The governor is the other big round thing.  The interrupter switch is sitting alone. 

 

Here's my car: 

 

 

 

Edited May 11, 2016 by DonaldSmith

[Stevenlesser]

The tip tow is a 2 speed trans with an overdrive for the upper range ,so lo hi and hi with a overdrive ,your colomb lever controls the upper and lower range hi and low

There's a kick down switch on the carter carburetor to go out of the overdrive if you need the power and ask for it by stomping the pedal

Conversely if you push on the throttle to accelerate and pull your foot and coast off it'll dump it into overdrive

It's a happy slo mo clunk that's hard to miss

The idle is supposed to be 450 or so so if it's setby a mechanic to a modern number like 1000 rpm the system gets fooled

There's a wiring harness with a couple of lines from the carb ,and from A firewall mounted relay and from lines the dash that goes back to the transmission in the desoto a junction block is on the air cleaner support

There's a governor and a solenoid,all over drives work this way the governor runs the solenoid ,it's just a switch that turns on at a certain speed and activates the solenoid which is just a switch that works by sticking out a rod

Try visiting desotoland site they're walking desoto-encyclopedias!

[mopar_earl]

M6 is a 4 speed with low and high range. Low is 1st and 2nd. High is 3rd and 4th. It automatically shifts up and down in each range. There is no overdrive. It's a 4 speed with direct 1:00 ratio in 4th gear.

Earl

[DonaldSmith]

So, it's actually overdrive technology (solenoid, governor, etc.) adapted to a four-speed transmission, operating as mopar_earl describes. 

[jharring10]

The wires on the carburetor cannot be reversed as there are two totally different connectors. One being a plug in and the other looks like a ground connection so it must be wiring. Where is the governor located? 

[jharring10]

Looks like DonaldSmith answered my question regarding governor location in an earlier post.

[dpollo]

Donald S.  has it right.   The M-6  if it can be called an overdrive can also be called an under drive.  To avoid any confusion, it cannot be compared with a Borg warner planetary OD like the R10.

 

 As I recall, there are three connections on the carb and two have bullet type ends so it is possible to reverse them.  The coil on top of the carb is energized at idle when the car is in gear to enrich the mixture so there is less chance of stalling or stumbling.

 

The electrical controls to the M6 only serve to kick the unit down.  It will perform just fine without the electrics but the downshifts have to wait until the vehicle comes to a halt.   

[jharring10]

I think it is possible that I might have what looks like a ground connection connected in the wrong location. Does anyone have a pic of what is similar to my carb to compare. Here is a pic of what I have and how it is connected.

[DonaldSmith]

Can't tell what color your wires used to be.  Possible the two wires to the anti-stall are one from the relay and one to the solenoid; should be red. 

 

Here's the top of my carb (Wiring WRONG!  Should be the RED wires.)

 

 

The other side of the carb (wiring correct):

 

 

[jharring10]

The first picture is the front of the carb with the two wires disconnected. Notice the arrows that point to where they are now connected. I should have taken a pic before I removed the carb to have it rebuilt. As you can see the connectors are a difference type so they cannot be reversed.  The connection that I labelled #1 is pretty obvious as it can only go one place. I think that the connection labeled #2 may be the issue. However, there is not much slack on the harness to go anywhere else. I have also included a pic of the front of the carb but cannot see any other connections.

Edited May 11, 2016 by jharring10

[DonaldSmith]

My car doesn't have that wire grounded to the carburetor.  Maybe trace your ground wire back.  Someone may have added it in ancient history . 

[Dodgeb4ya]

The forked connector wire (#2) connects to the screw on the kick down plunger switch--NOT to ground.

If you ground it the car will never up-shift!

Edited May 13, 2016 by Dodgeb4ya

[DonaldSmith]

Bingo!

[jharring10]

Lesson learned for not taking a pic as to how it was previously connected.  Some are saying that both wires go into the two terminals on the anti-stall but one of the connections appears to be broken. See pic as I have circled the one that appears to be broken but based on other posts it is normal.  When you refer to the kick down plunger switch are they the same thing just different terminology? The forked connection does not have slack to go a lot of different locations. I have been working on this issue for a couple of years now and I feel that I am running out of options. Very frustrating.

Edited May 12, 2016 by jharring10

[DonaldSmith]

See Post No . 22.   Do you have another wire going to the kickdown switch, or should the grounded wire go there?  Trace where the wires go.  A wiring diagram is invaluable.

 

The 1949 and later transmissions have a different wiring setup, which has two wires connected to the anti-stall. My car, a 47, has two terminals at the anti-stall, but only one is used.