Kickdown fine tune adjustment

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340inabbody

340inabbody

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Got the 904 with the 340 kickdown adjusted for the 3-2 downshift nicely. Where can I find information on how to finally tune it for the 2-1 downshift? Or can anyone explain how that gets done once it set up for 3-2 downshift? Should I bring it a bit sooner? It’s not like there’s multiple handles here.
 
Bewy said:
I would think the governor plays a part in the shift points.
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Yes it does. I am referring to kick-down or passing gear as it used to be called. I am new to vintage automatics. Wondering also if there is actually a 2-1 kickdown. After watching the video I am questioning it .
 
Do you know the year of the 904 ? I believe that 71 was the first year for part throttle kick down.
I may be wrong so don't hold me to it. Before that kick down was only under full throttle.
It sounds like you question is, say you are rolling at 20 mph and the transmission is in 2nd will it kick down to 1st when you press the accelerator . It is my understanding that the kick down overrides the governor pressure in the valve body
till set rpm allows the governor weight to override the kick down.
 
Darter6 said:
Do you know the year of the 904 ? I believe that 71 was the first year for part throttle kick down.
I may be wrong so don't hold me to it. Before that kick down was only under full throttle.
It sounds like you question is, say you are rolling at 20 mph and the transmission is in 2nd will it kick down to 1st when you press the accelerator . It is my understanding that the kick down overrides the governor pressure in the valve body
till set rpm allows the governor weight to override the kick down.
Click to expand...
It’s a 1970 I believe. Yes the question is now is there any kick down effect from 2-1? Watching the Chrysler video is indicating no. I was told yes but see no way to adjust for it unless its from the actual geometry. If thats the case I am screwed as my kick down setup is slightly modified.
 
340inabbody said:
Got the 904 with the 340 kickdown adjusted for the 3-2 downshift nicely. Where can I find information on how to finally tune it for the 2-1 downshift? Or can anyone explain how that gets done once it set up for 3-2 downshift? Should I bring it a bit sooner? It’s not like there’s multiple handles here.
Click to expand...
There's only one adjustment so you have to find a happy medium between the 2.
 
There's more than one adjustment but you have to take the pan off to get to the other one. The way I always adjust it is as follows.

Adjust the linkage so that the lever at the transmission is all the way BACK with the gas pedal on the floor. Then drive it and see how it is. If it holds the gear out too long, then adjust the linkage a little shorter and keep trying it. Also, it might be a good idea to make SURE the carburetor is WIDE OPEN with the gas pedal on the floor. If it's not, make that adjustment FIRST and then adjust the kickdown linkage as I described.
 
340inabbody said:
OK so are you saying the the kick down valve DOES affect the down shift or kick down from 2-1?
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The adjustment inside the pan affects both shifts, because it changes line pressure. But make all your adjustments on the outside FIRST and go from there. If you do have to remove the pan, it will be easy to see if you have the part throttle kickdown on the valve body.
 
RustyRatRod said:
There's more than one adjustment but you have to take the pan off to get to the other one. The way I always adjust it is as follows.

Adjust the linkage so that the lever at the transmission is all the way BACK with the gas pedal on the floor. Then drive it and see how it is. If it holds the gear out too long, then adjust the linkage a little shorter and keep trying it. Also, it might be a good idea to make SURE the carburetor is WIDE OPEN with the gas pedal on the floor. If it's not, make that adjustment FIRST and then adjust the kickdown linkage as I described.
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Yes this is exactly how I adjusted mine. Thank you.
 
And yes, the kickdown adjustment most certainly does affect the shift both up and down.
 
It’s shifting to second to quickly. What can I do other than change the governor to extend the shift more from 1-2?
 
If you end up removing the pan, you can see if it has the part throttle kickdown valve assembly. Look at the red "circle". That's it. If there's just a flat plate there, you don't have it.
VALVE BODY.jpg
 
340inabbody said:
It’s shifting to second to quickly. What can I do other than change the governor to extend the shift more from 1-2?
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Give it more throttle pressure. Have you checked to see if the carburetor is wide open with the pedal on the floor? It's important you do that FIRST, otherwise all other adjustments will be off.
 
RustyRatRod said:
Give it more throttle pressure. Have you checked to see if the carburetor is wide open with the pedal on the floor? It's important you do that FIRST, otherwise all other adjustments will be off.
Click to expand...
Sorry stupid question. When you say give it more throttle pressure are you meaning to adjust the kick-down to apply more pressure?
 
340inabbody said:
Sorry stupid question. When you say give it more throttle pressure are you meaning to adjust the kick-down to apply more pressure?
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Start there, yes. But DO what I recommended FIRST and check to make sure you are getting full throttle with the gas pedal. If not, fix that FIRST.

Now, if you end up needing to adjust the actual throttle pressure at the valve body, here is how you do it. Don't worry about the "special tool". The factory spec is 5/8" between the end of the throttle valve and the lever. Adjustment is made by turning the allen head screw clockwise to increase and counter clockwise to decrease throttle pressure. It's not uncommon AT ALL to have to adjust so that the space between the throttle valve and lever is different from spec, due to many variables. So if you end up having to get the pan off and you see you need to go less than 5/8" that's fine. The space is measured between the two red lines. I always adjust more throttle pressure than spec (less than 5/8") and then I can adjust everything using the outside linkage. Most people want to firm up the shifts some anyway and that will give you the freedom to do so.

VALVE BODY ADJUSTMENT.jpg
 
RustyRatRod said:
Start there, yes. But DO what I recommended FIRST and check to make sure you are getting full throttle with the gas pedal. If not, fix that FIRST.

Now, if you end up needing to adjust the actual throttle pressure at the valve body, here is how you do it. Don't worry about the "special tool". The factory spec is 5/8" between the end of the throttle valve and the lever. Adjustment is made by turning the allen head screw clockwise to increase and counter clockwise to decrease throttle pressure. It's not uncommon AT ALL to have to adjust so that the space between the throttle valve and lever is different from spec, due to many variables. So if you end up having to get the pan off and you see you need to go less than 5/8" that's fine. The space is measured between the two red lines. I always adjust more throttle pressure than spec (less than 5/8") and then I can adjust everything using the outside linkage. Most people want to firm up the shifts some anyway and that will give you the freedom to do so.

View attachment 1716342470
Click to expand...
This is good info
 
If you want to increase the 1-2 upshift speed, you can do it without removing the pan.
If you have a carb with large throttle bores, it requires less throttle opening than a carb with small t/bores....to get to the same road speed [ shift speed ]. The K/D lever moves less with a big carb, all else being equal; & the trans shifts earlier, all else being equal.
The above demonstrates that it is a 'ratio thing '.

If you want later shifting: there is a rod from the carb that goes to a bracket/linkage at the back of the engine. Where this rod hooks onto the bracket, the hole or stud on that bracket needs to be repositioned closer to the pivot.
The idea is: for the same throttle open position, the K/D lever moves further, increasing line pressure & delaying the shift point. You might need to experiment with different hole positions. The same thing can be achieved with the K/D lever on the trans; move the linkake hole closer to the pivot.
 
Bewy said:
If you want to increase the 1-2 upshift speed, you can do it without removing the pan.
If you have a carb with large throttle bores, it requires less throttle opening than a carb with small t/bores....to get to the same road speed [ shift speed ]. The K/D lever moves less with a big carb, all else being equal; & the trans shifts earlier, all else being equal.
The above demonstrates that it is a 'ratio thing '.

If you want later shifting: there is a rod from the carb that goes to a bracket/linkage at the back of the engine. Where this rod hooks onto the bracket, the hole or stud on that bracket needs to be repositioned closer to the pivot.
The idea is: for the same throttle open position, the K/D lever moves further, increasing line pressure & delaying the shift point. You might need to experiment with different hole positions. The same thing can be achieved with the K/D lever on the trans; move the linkake hole closer to the pivot.
Click to expand...
That makes sense. Thank you for explaining this. Il be working at this over the next few days and will report back my findings.
 
When you have it adjusted properly, under normal driving conditions, it should shift from 1-2 at 18 mph and from 2-3 at 28 mph. If it is short shifting (too early) make the rod longer by unscrewing the adjustment at the carb. If it is holding too long and shifting late, shorten that same adjustment a few turns at a time to get it dialed in. Obviously, the more you mash the gas pedal, the more throttle pressure the valve body sees and will hold shifts longer, as it is designed to do. You do not want to lengthen the throttle pressure linkage to the point that it keeps the carb butterflies from achieving wide open throttle, like @RustyRatRod advised above. It is also important to have a small spring pulling the throttle pressure linkage forward towards the carb stud that pushes it backwards. If there is a gap between the stud on the carb and the linkage slot, the valve body isn't seeing any pressure applied from idle to wherever the stud finally catches the slot and starts pushing. Go back up to post #2 and look at the pic. See that little triangle shaped tab welded to the kickdown rod? The little spring goes in the hole in that tab and hooks to the end of the carb stud to hold the adjuster to the rod at all times. Keep plugging at it, and you'll get it figured out.

:thumbsup:
 
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