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Fluid Drive Stalling


51_Meadowbrook

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I have a 1951 Dodge Meadowbrook with the standard 3 speed transmission fluid drive. When it is idling in neutral it runs around 450-500rpm. When I put it in gear and take out the clutch the engine bogs down to around 200-250rpm. I have changed the fluid with the TDH ISO32 like many of the forums here have said to do and it still does it. When I try to take off with the clutch out it either stalls or stumbles for about a second then takes off. When I am rolling down the road it runs and shifts fine with no hesitation. When you have it in gear with the clutch out, lets say in second gear, and you release the brake without pushing the accelerator it pushes the car forward like it would in an automatic transmission. Is the engine supposed to lower rpms when in gear with no clutch and no acceleration? Is something getting hung up and causing it to act like a normal standard transmission?

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It sounds like everything is fine except you might safely increase the idle speed.  The fluid drive is not a torque converter so acceleration from a standstill in High gear can only be described as "majestic".  As for creeping forward, for reasons of safety, the transmission should be put in neutral if the car is left idling with the clutch engaged.

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It sounds like it’s working normal. You could bring your base idle up to 600 and that will help. Also, fine tuning the idle mixture screw can have a positive effect on your loaded idle. 

Also, you may already know, but be sure your park brake is functional and ALWAYS use it when leaving the vehicle unattended. With no mechanical link between the engine and the wheels the vehicle can roll even when left in gear. 

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"Majestic."  I like that.  I never thought to even include a description in the same sentence as acceleration, but "majestic" is cool.   I'll echo the previous posts, it sounds like you car is running as it should.  If you're driving it with the clutch all the time, you should drive it like a regular manual tranny car - gas with clutch release.  But the fluid-drive is intended to reduce clutch use, and in some cases eliminate it.  Once you get going you really don't need the clutch anymore, and the car's idle will be noticeably below the unloaded idle speed.  Driving around town, I'll leave it in second, otherwise once I get to third, I leave it there.  Because there is no mechanical link, the car shouldn't outright die, but there is load, so the idle will slow down below unloaded idle speed when stopped with the car in gear, and no clutch.  The carburetor has a retarded throttle return so the car doesn't die when you come to a stop, it allows time for the fluid-drive to even itself out.  I set my "regular" idle at 600 rpm as Merle suggests, but that's more for my assurance than the car needing it. 

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Based on the book the engine should idle at 450-500rpm. The car is obviously not running just fine or it wouldn't be stalling when you attempt to take off in gear. When it is idling and you press the accelerator it stumbles then revs. The carburetor has been rebuilt 2 months ago and it is acting just the same as before. The timing is just before TDC like the book says. Even in high gear it should not stall, it should just take off slowly. If I rev the engine in neutral to 600rpm its going to scream every time I come to a stop and push the clutch in. I don't want to mask a potential problem by raising the idle. The compression in the engine isn't great but its not terrible. The shop manual says that with all the plugs out and the throttle wide open the compression should be 120-150. This is how mine read:

1: 85

2: 90

3: 92

4: 92

5: 100

6: 100

 

The compression test was completed twice with the same results.

 

Could a vacuum leak in the intake manifold cause the stumble at initial acceleration? Could it run itself too lean and then straighten out?

Edited by 51_Meadowbrook
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I have Fluid Drive in my truck, with a 4 speed, and I went through this issue too. 600 RPM no-load idle will not make it scream when coming to a stop with the clutch depressed. If it does then its the dashpot in your carb that is holding the throttle open too much. Mine is adjustable and I backed it off so that it really doesnt’ do anything anymore. I don’t have any issues with stalling if I stop without depressing the clutch. 

 

Upping the idle to 600 ish really helped me. If you’re not comfortable with that, bump it up to 550. Also, as I mentioned earlier, fine tuning the idle mixture also helped a lot. And be sure that your accelerator pump is working properly. I also have my ignition timing set to 2-3 degrees BTDC which also aids the throttle response. With the engine up to temp, back the idle down around 300, then play with the idle mixture screw to find the best running. Then turn the idle back up. I find it’s easier to notice the changes at lower idle speeds. Also tweak the timing a little, readjust the idle speed, etc., until you find the sweet spot. 

 

As like was mentioned earlier, I will leave mine in 3rd around town, using brake and gas only. Then shift up to 4th when things open up a bit more. Launching at a green light in 4th is possible, but slow. I also like the “Majestic” reference, but I don’t know if that’ll work with a truck. :D  I just can’t picture my truck as Majestic. 

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What carb is on it... Stromberg or Carter?

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It’s a Stomberg BVX. The book says I should have the BVXD-3 but it didn’t come with it so I don’t have a dashpot. I used a timing light and have the timing a few ticks BTDC and the gaps are right to the best of my ability. The stumble happens even when I am in neutral unless I open the throttle extremely slowly. I checked the vacuum advance and it operates like it should. 

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Is the throttle shaft tight to the throttler shaft operating lever?

On the BVXD-3 the side lever comes loose from the throttle shaft and causes erratic idle speeds regardless of the idle speed screw.

Of course this will not affect the hesitation issue.

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If it stumbles when opening the throttle while the transmission is in neutralit sounds like your accelerator pump is not working.  With the engine off and the air cleaner removed, look down into the throat of the carb. When you open the throttle you should see a healthy squirt of gas.  If you don’t see a noticeable strong stream of gas, your accelerator pump is not working properly.  I know that you said that the carb was rebuilt, but if the rebuild kit was old the accelerator pump piston could be dried out.

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 have corrected the accelerator pump issue that I did not know I was having. The throttle shaft was wiggling where the linkage connects. I secured it. The accelerator pump was not going up enough for it to get a long stream, it stopped about halfway through the throttle opening. I added a couple washers that are the size of the linkage so it won’t bind. Now when idling and the pedal is pressed it revs beautifully. I increased the idle to 700rpm and when I put it in gear and released the clutch it dropped down to 350rpm. I  released the brake, pushed the accelerator, and.... it stalled. So I started it again, put it in gear, released the clutch (dropped to 350rpm again), I pushed the accelerator very very slowly so it started to raise the rpms, released the brake and it took off very slowly. So obviously the issue is that the engine drops too low in gear when stopped. How do I correct that? Even at 700rpm idle it dropped in half. So does that mean I need to put the idle at 800-900 to get 400-450 in gear at stop? I know that can’t make sense to do. 

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Been watching this thread progress but I have to wonder if you put the wrong fluid or too much in you FD unit.  My 49 drops about ~100 RPM when I release the clutch at a stop and as far as I know the fluid has never been changed.  My idle is set about 500 RPM unloaded.  Maybe drain an inch of fluid out of the FD unit and give it another go?  Or try thinner fluid? 

 

Adam

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I filled the FD with the hole at 2 o’clock until it weeped out. If I lower the fluid level it will lower the pressure I’m assuming. So you are saying that the pressure built up is going to cause too much strain on the “coupling” and drop the engine rpms?

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I'm saying to try to run it a little low and see if it slips more, especially at idle.  Can't see and inch or 2 low causing any damage but worth a try....  I also heard the ISO 32 fluid is thicker than the original stuff.  Then there was the ISO 22????  hard to find stuff??  Sorry my memory isn't what it used to be.

Does the engine seem to have enough power once you get past the stumble?

Edited by Adam H P15 D30
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I"m using ISO 32 oil in my FD and it works fine.

Maybe the issue has to do with being the wrong carb. I don't know what the differences are in what you have and what was originally there. But I'm going to stick with my suggestion to adjust the idle mixture and see what happens. If the adjustment doesn't change the idle then that circuit may be clogged up along with your accel pump circuit. The dashpot should only affect the return to idle from higher RPM.

Edited by Merle Coggins
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4 hours ago, Adam H P15 D30 said:

I'm saying to try to run it a little low and see if it slips more, especially at idle.  Can't see and inch or 2 low causing any damage but worth a try....  I also heard the ISO 32 fluid is thicker than the original stuff.  Then there was the ISO 22????  hard to find stuff??  Sorry my memory isn't what it used to be.

Does the engine seem to have enough power once you get past the stumble?

I had a tough time finding the ISO 32. They didn't have the ISO  22. 

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6 hours ago, 51_Meadowbrook said:

I use the TDH ISO 32 that everyone says is the closest to Mopar Fluid Drive fluid. When I drained the FD it looked like standard 10wt oil. When I drained the transmission i found this.. 

2C373ED2-3F4D-45D5-8125-8B64C46790B1.jpeg

looks like you are draining the 3 speed  transmission here... not the FD coupling. Hope you drained and re-filled both the trans and the FD coupling with the correct fluids the correct way.

 Just fill the FD coupling till it runs out of the small fill plug hole in the coupling at 2 O'clock.

It won't build up excess pressure or anything scary.

Edited by Dodgeb4ya
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I found that a lot depends on how well the carb is set up. I have a FD 3/4 ton truck similar to Merles. When I first put it on the road it felt like it was going to stall when using the fluid drive feature so I just drove it like a regular stick. Also it didn't really feel right under acceleration. A few months in and I decided to go through the Carter carb again and while I was at it I replaced the step up jet. Bingo! apparently the step up circuit was the culprit all along. After this carb rebuild the truck ran much better and using the fluid drive was no longer an issue. BTW the carb I was using was a complete NOS model that had never been fitted to anything. I have no idea why changing the jet made such a difference but it did. Just something to chew on.....

Jeff

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I’m going to assume that the carburetor is faulty. Unfortunately I’m a self learned man and don’t know all the tricks to the beast. If it is in gear and I press the accelerator normally to take off it either stalls or it stumbles then takes off. If I press the accelerator so slow it takes 30 seconds to get up to 15mph then accelerate normally it doesn’t stall or stumble. If I punch the accelerator it doesn’t stall or stumble. I know everyone is going to keep saying “it’s the accelerator pump” but is it definitively that or is there something else that might have that as a symptom too? I’m guessing that it’s leaning out if I press the pedal normally before enough gas is pumped into the intake.

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2 hours ago, 51_Meadowbrook said:

I know everyone is going to keep saying “it’s the accelerator pump” but is it definitively that or is there something else that might have that as a symptom too? ....

 I don't know why you are stumbling around with this question . it is a quick and easy question to answer . The only thing you need to do is take off your air cleaner , and with the engine off , shine a light down into your carburetor . Give the throttle linkage a full stroke and you should see a strong shot of gas going into the carb . If you don't see the strong shot of gas and your carb has gas , then you need to work on your accelerator pump . It is simple , just do it . 

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Back to basics on this one.....assuming you have a solid carb, dashpot as needed and no binding in the FD/trans/drive line, etc....

 

 

I would look for a vacuum leak, possibly including throttle shaft, manifold, valve guides, vacuum wiper port, vacuum canister, vacuum advance diaphragm leaking, etc.....get out the vacuum gauge and see if you have at least 16" steady at warm idle and see what it does reving and also while under load driving (longer hose needed) and squirt every joint and hose with carb cleaner and note changes in idle speed, normal checks....

 

Or you have an ignition issue, like too much or too little timing, slipped balancer, stuck mechanical advance, vacuum advance not working/perforated, points too wide/narrow, wires, plugs, coil, condenser.........

 

One step at a time, get ignition and vacuum vetted first since it at least runs, then work your way through fuel to FD, other possible causes.

 

Luck.

Edited by Sharps40
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