727 jumping shift detents

[Jay E.]

I am manually shifting my 340 at the drags. At anything less than full throttle, the 1-2 shift is clean. But when the gas is fully mashed it has a tendency to jump 1-3, or even (heaven forbid) 1-N. I am very deliberate when I shift and it isn't a matter of my getting overexcited and moving it too far.
The detents are very soft, so it is pretty easy to over shift. At full throttle I can't seem to make it consistent. The 2-3 shift is fine.
Is there a way to make the detents stiffer, or have some kind of gate do there is a more deliberate feel to the column linkage?
The linkage isn't sloppy but the feel in the detents is soft.

I'm not exact sure how to ask this question as the upshift in the transmission is very crisp. Just the detents seem sloppy or soft.

 

[Locomotion]

It's been a while but if I remember correctly and understand your problem.....the spring that puts pressure on the detent ball that rides against the shift lever "comb" may have broken.

I've seen the same thing happen inside neutral safety switches.

For manual shifting/performance use, it's always safer to have an aftermarket shifter with its own detents for precise engagements as well as a reverse lock-out.

 

[Jay E.]

Thank you for the image. it is helping me to visualize the issue. Is there such a thing ( Aftermarket detents) for a column shift? It is possible that the part with the Z is worn too? I wonder if there is one that has deeper indents? Is it hard to access this in the tranny, can it be seen if the pan is dropped?

 

[Demonx2]

I am manually shifting my 340 at the drags. At anything less than full throttle, the 1-2 shift is clean. But when the gas is fully mashed it has a tendency to jump 1-3, or even (heaven forbid) 1-N. I am very deliberate when I shift and it isn't a matter of my getting overexcited and moving it too far.
The detents are very soft, so it is pretty easy to over shift. At full throttle I can't seem to make it consistent. The 2-3 shift is fine.
Is there a way to make the detents stiffer, or have some kind of gate do there is a more deliberate feel to the column linkage?
The linkage isn't sloppy but the feel in the detents is soft.

I'm not exact sure how to ask this question as the upshift in the transmission is very crisp. Just the detents seem sloppy or soft.

Stock floor shift?

 

[Locomotion]

You would have to carefully remove the valve body to see the top, as in the photo. I never heard of any mods to the OEM detents or OEM shift mechanisms. But you would need to find the correct spring in the valve body, if that's part of the problem.

You should be concerned about the trans upshifting or downshifting a gear when you don't want it to. Aftermarket shifters work with the OEM valve body for precise control. Although some people do it and some are pretty good at it, it's still risky. An aftermarket shifter is not only safer but will likely be more consistent as far as your shift points are if you're bracket racing. One less distraction you so you can focus on cutting a light, hitting your shift points and judging the finish line.

 

[Jay E.]

Until I get this figured out I am just going to put it in D and mash the gas and let it do the shifting. I like to use the column shift because it shifts out of 1st before it gets to the sweet spot in RPM for second.

Do others with a 340/727 shift manually or let the tranny do the shifting?

 

[AJ/FormS]

The roostercomb has it's own detent system
The Column has a neutral/reverse/park gate
These two have to be synchronized; and an adjuster-bolt is/or should be, provided on the downrod under the hood or under the chassis.
So this reminds me that the weight of the column shifter may be telegraphing thru the linkage and into the rooster comb, so, I would do what I could to alleviate that first.
Next; is it possible that your engine mounts are allowing the engine/transmission to twist enough to allow the gates to become un-synchronized?
I would check the mounts, and if that's not a problem, then I would just put a stiffer spring on the roostercomb. But, doing so is like installing a double-edged sword. A stiffer detent makes you tug harder on the column-shifter, increasing the risk of overshifting. So, that's something I'd leave for last resort.
My money is on;
1) the engine/trans moving around or
2) chassis-flex/frame-flex, and/or
3) the column shifter flopping around down on the bottom.
4) vibration; if the tailhouse or the main-housing, is jumping around, that is gunna directly telegraph to the shift rod.
Since you mention downshifting, don't forget that on deceleration, the Pinion gets ripped downwards towards the road, pulling the driveshaft out of the tailhouse.... making the front U-joint move backwards toward the rear. If it comes out too far, it may set-up it's own vibration, which I suppose could set up something in the Transmission mount, which, again, is gunna telegraph into the roostercomb and from there, into the shift-rod. So there are a couple of more things to check.

The point is this; the trans has to stay where it was, when the gates were synchronized.
With a column shifter, if things move around, there will be trouble.
With a floor mounted cable-shifter, that is anchored to the trans, this should stop.
Even the factory console shifter, as sloppy as it may be, it works because of the comparatively light-weight rods and lack of kinetic energy being transmitted to the roostercomb.

 

[Bewy]

I am with AJ. You could have a movement/flex problem whereby the linkage is moving the shift lever...when it shouldn't be.

 

[Jay E.]

The roostercomb has it's own detent system
The Column has a neutral/reverse/park gate
These two have to be synchronized; and an adjuster-bolt is/or should be, provided on the downrod under the hood or under the chassis.
So this reminds me that the weight of the column shifter may be telegraphing thru the linkage and into the rooster comb, so, I would do what I could to alleviate that first.
Next; is it possible that your engine mounts are allowing the engine/transmission to twist enough to allow the gates to become un-synchronized?
I would check the mounts, and if that's not a problem, then I would just put a stiffer spring on the roostercomb. But, doing so is like installing a double-edged sword. A stiffer detent makes you tug harder on the column-shifter, increasing the risk of overshifting. So, that's something I'd leave for last resort.
My money is on;
1) the engine/trans moving around or
2) chassis-flex/frame-flex, and/or
3) the column shifter flopping around down on the bottom.
4) vibration; if the tailhouse or the main-housing, is jumping around, that is gunna directly telegraph to the shift rod.
Since you mention downshifting, don't forget that on deceleration, the Pinion gets ripped downwards towards the road, pulling the driveshaft out of the tailhouse.... making the front U-joint move backwards toward the rear. If it comes out too far, it may set-up it's own vibration, which I suppose could set up something in the Transmission mount, which, again, is gunna telegraph into the roostercomb and from there, into the shift-rod. So there are a couple of more things to check.

The point is this; the trans has to stay where it was, when the gates were synchronized.
With a column shifter, if things move around, there will be trouble.
With a floor mounted cable-shifter, that is anchored to the trans, this should stop.
Even the factory console shifter, as sloppy as it may be, it works because of the comparatively light-weight rods and lack of kinetic energy being transmitted to the roostercomb.

I agree with your assessment that something is twisting when there is a lot of torque and possible affecting the linkage and causing the overshift. I'm not sure how to check the motor mounts, they are new but that doesn't mean much. Ill put a jack under each one and make sure they are solid.
I've been through all the linkage points and they are as good as they can be, which is to say nothing like a cable. I understand it a lot better now that I see the rooster tail.
I suspect the detent spring is worn or broken as it is quite a soft movement, just fingertip for about 1 or 2 inches of movement per detent.

 

[AJ/FormS]

I suspect the detent spring is worn or broken as it is quite a soft movement, just fingertip for about 1 or 2 inches of movement per detent.

I've been through all the linkage points and they are as good as they can be,

Are you saying that the lever on the transmission has 1 or 2 inches of movement before it clicks to the next detent? Cuz that would speak to a broken rooster comb..
But if yur talking about the shift lever on the column, then you got serious problems, that need to be sorted out. You can't race like that! I would start by looking at the bottom-of-the-column bearing. Followed by the various bushings and pin-holes, and ending at the top of the column under the steering wheel. Or even simpler, what's retaining the column lever?

 

[Jay E.]

I was describing that it only takes a very small movement to shift it between detents. It is very light pressure. I don't need to grasp it and move it until it is into Reverse.
There is nothing loose in the linkage. It just moves very easily between the detents.

 

[Ricks70Duster340]

Sonnex has a kit that replaces the ball & spring that controls the rooster comb. After awhile, the steel ball wears into the softer aluminum and things get sloppy.

 

[Jay E.]

Very good, thank you for that information! Im not sure that this is the issue as I have no issue with alignment or shifting into park or starting. But I will contact them
From Sonnex" The detent ball in the valve body in listed Chrysler transmissions wears into the aluminum bore due to continuous movement and vibration of the linkage. This creates excessive looseness in the manual valve lever and allows the manual valve to move out of alignment. No start or being stuck in Park can occur from the manual valve being out of position due to extra clearance"

 

[Bewy]

With a column shifter, you get a lot of leverage simply from the length of the lever. So the action will probably feel light.

 

[Michael Siple]

A sloppy column / collar like ours doesn't help - in need of rebuild & I think maybe it will clean things up a little.