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Purpose Of the kick-down spring

Moparfiend

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Merry Christmas all!!!

Hey Mopar die hards who are here on this forum today looking for your input on this mystery to me.

Does the geometry of the kick down spring fight agsinst the throttle return spring? I don’t think it does for the 1970 Satellite 2 barrel carter set up. Mine was missing and most of the documentation I have seen is mixed. Meaning that I have seen spings pulling in both directions. I believe the correct geometry is throttle connection towards the fire wall on the kicksown bar itself. I have converted to using a Street Demon 4 barrel and have the linkage adjusted but need to add a return spring.

If this is the case then does it pull the kickdown lever towards the front of the car keeping the kickdown lever engagement to the throttle bar? If so does this create a safety issue as it pulls against the throttle return spring towards WOT?

Or is the kickdown spring just an anti-rattle spring and does not pull the throttle to WOT?
 
The kickdown rod is supposed to be kept forward when the throttle is in the closed position and it moves 'with' the throttle when it's depressed. When things are adjusted properly, the transmission will see the pressure it's supposed to as the throttle and kickdown moves back as you accelerate. And Merry Christmas to you too!
 
The way the linkage is now set up my Kick-down is fully engaged (back and down at WOT). This is based solely on the linkage engagement and not any springs. This should open the valve on the trans fully for maximum pressure. This I understand and have accounted for.

My question is what is the purpose and function of the kickdown linkage spring and is it working against the throttle return spring?
 
Re-read Crankys post. The springs don’t fight each other.
 
As cranky said above. The spring in the factory location looks like it works against the throttle shaft return spring,but regulates the return of the kickdown rod and pulls it back as the throttle closes.In the photo below I used the 2 bbl linkage when I installed the 4 bbl.I made a tab and ran the spring forward like the throttle return springs.
Clear as mud I know,,but works for me.I hope this helps.

IMG_2649.jpg
 

About 1:35 it'll show how the spring is supposed to be from the factory. And right, the KD spring isn't fighting against the throttle return spring at all. In fact, it really doesn't do much besides making sure the KD linkage stays and moves with the throttle lever. Many hook up the KD spring with the throttle spring and that'll work too.....just so long as the KD linkage stays against the throttle rod.
 
Picture 066.jpg
The way the linkage is now set up my Kick-down is fully engaged (back and down at WOT). This is based solely on the linkage engagement and not any springs. This should open the valve on the trans fully for maximum pressure. This I understand and have accounted for.

My question is what is the purpose and function of the kickdown linkage spring and is it working against the throttle return spring?

The spring keeps the arm forward to regulate throttle pressure,without the spring you can kiss your transmission goodbye in a short period of time.There are a multitude of ways to make it work depending on linkage
 
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You can see the KD spring pulls the rod forward. The spring is lighter than the throttle return spring. The kickdown lever on the trans has freeplay before hitting resistance as the throttle is depressed. Without the spring the KD would float and cause some weird trans issues.
15141436282601466438105.jpg
 
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yep , im "that guy" ....I'm not advising in any shape or form , but I have known guys who have tied the KD arm 1/2 to 3/4 of the way back on the trans and have put thousands and thousands of miles on their stock 727's without any kind of failures. in fact I have one of them as a spare right know that was shifting like a beast when pulled. so all this "you'll barbeque your trans in short order " without the TP hooked up is simply not true.
 
Well, explain why mine didn't hold up when that was done.
 
Thanks Threewood! Merry Christmas to ya!

By forward you guys are all meaning towards the front of the car when the throttle is closed yes?

That makes sense.

Adjustments are a little tricky and here is why from my perspective. There is more lever action including freeplay travel in my kickdown/transmission. Also toward the end towards the back on the kickdown there is resistance the throttle lever needs to overcome.
 
Thanks Threewood! Merry Christmas to ya!

By forward you guys are all meaning towards the front of the car when the throttle is closed yes?

That makes sense.

Adjustments are a little tricky and here is why from my perspective. There is more lever action including freeplay travel in my kickdown/transmission. Also toward the end towards the back on the kickdown there is resistance the throttle lever needs to overcome.

Yes, forward toward the front of the car. The kickdown plunger and spring in the transmission as set with freeplay. So, if you remove the rod from the carb and work the KD back with your hand you can feel that slack before hitting the spring tension. That is by design. Why? I have no idea but I have rebuilt a few and they all have free play.keep the KD forward with the spring to stay in contact with the throttle so the KD doesn't float. Earlier variations didn't have a slot in the rod, only a cup that fit over a ball mount on the carb lever. So no extra spring was needed.
 
OK this makes sense from all the great information above.
Let me see if I can summarize.

The kickdown spring is of lesser force than the throttle return spring. The purpose of the kickdown spring is to maintain engagement of the kickdown to that of the throttle in such a way as not to work against or for the throttle return spring. This engagement relationship is needed to maintain proper throttle and transmission kickdown valve setting for different throttle positions. The kickdown should follow the throttle movement. At WOT the kickdown should be fully engaged (directly by the throttle lever) back without binding the throttle. At off throttle the the kickdown spring should insure that the kickdown follows the throttle forward lowering the effective kickdown on the transmission for idle and off idle conditions.

How is this? Is this explanation accurate and complete?
 
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Sounds like you got it.If you have a service manual or find it on line there is a procedure for proper adjustment.Or like many do adjust to your liking,lets say 1-2 shift at 15 mph(Light throttle)2-3 shift at 25 mph.It can be achieved sooner or later by adjusting the threads to make the rod longer or shorter.Again clear as mud.....
 
Sounds like you got it.If you have a service manual or find it on line there is a procedure for proper adjustment.Or like many do adjust to your liking,lets say 1-2 shift at 15 mph(Light throttle)2-3 shift at 25 mph.It can be achieved sooner or later by adjusting the threads to make the rod longer or shorter.Again clear as mud.....
Yup....you can do it like that but make sure the KD doesn't bottom out before full throttle does. You can even adjust that problem with an adjustable rod going down to the trans....
 
Well, explain why mine didn't hold up when that was done.
I could see if the tp was just left idle and wasn't delivering adequate line pressure by being pulled back , maybe it was just coincidence I don't know, I was only relaying my experience, I'm by no means an trans-expert . I certainly wouldn't tell anyone it's ok to do it but I've never seen evidence that it's detrimental
 
If the kick down rod is too far forward when you are driving, then the transmission will run away, when it's shifting under part throttle pressure. When the rod is farther back, then it will shift quicker and harder. So you do want the spring hooked to the linkage, or it will shift too hard at part throttle, and at too high of an RPM.
 
If the kick down rod is too far forward when you are driving, then the transmission will run away, when it's shifting under part throttle pressure. When the rod is farther back, then it will shift quicker and harder. So you do want the spring hooked to the linkage, or it will shift too hard at part throttle, and at too high of an RPM.
Hi Gary, so thats a linkage adjustment more than how the actual linkage is set up correct? And the linkage adjustment is done by the upper ans lower ball cranks thereaded rods correct?

Here is how mine is set up. I am awaiting my kickdown spring and will install that when I get it.

Thoughts?
7ED2AB57-55DD-4667-9782-978CCAA2C6D3.jpeg
CDC25B45-D86B-4B70-9430-AD38EE5D463F.jpeg 450647D2-4574-46C0-986F-3E44E67C0D69.jpeg
 
Yup, you can use the threaded portions to take up ‘slack’ in any portion(ball-sockets) that have a little wear on them.
 
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