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Old 08-08-2022, 03:31 PM
tjs72lemans tjs72lemans is offline
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Default M40 downshift switch

My maiden voyage last year my downshift worked when I tromped on it. It's never worked since. It's the only thing on my whole frame off restore on my 72 Lemans vert that hasn't worked. I checked the wire terminal by accelerator pedal and the orange wire has power. Going under to the 400 auto trans there are two electrical connections. I assume the forward one on side or the one at rear by speedo cable is where I need to check for power again. The other switch must be wired to my TCS that I have unplugged and don't use. I did push the switch bar forward and then pushed accelerator pedal to floor to set as manual stated. Maybe my switch is bad or the one in tranny. Anyway, manual doesn't tell me where to check for power on tranny to see if above switch is working.

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Old 08-08-2022, 04:39 PM
tjs72lemans tjs72lemans is offline
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After I posted and read some related posts, I realized my tranny doesn't ever downshift even when going slower and accelerating faster. This tranny was rebuilt. I assumed it had a new modulator put in, but maybe it's the old one and doesn't work or needs adjusting or the governor isn't working. I'm not too familiar with trannys, so any help is good.

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Old 08-08-2022, 08:25 PM
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Sit in a quiet garage, key in run position; reach for and slide the kickdown switch, listen for a TH400 relay click.

Repeat for assurance.

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Old 08-08-2022, 08:29 PM
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Does this have the kickdown switch at the gas pedal? You have power TO the switch, do you have power THROUGH the switch when the gas pedal is stomped?

You likely need to re-set the initial position of the switch, since "pushing the switch-bar forward" is exactly what you do NOT want to do. You need to move the switch-bar REARWARD as installed, THEN push the gas pedal to WFO. You'll hear the "ratchet" of the switch parts self-adjusting as the pedal is close to WFO.





Sometimes the switches get sticky due to old grease. I pull 'em apart for cleaning, inspection, and fresh lube.




With the ignition "on", you should be able to hear the trans kickdown solenoid click when the pedal is pumped. No clicking = failed electrical including the adjustment; or a failed solenoid.

It's moderately common for the gas pedal to bend so that the carb does not truly go to WFO, and the kickdown switch doesn't get fully activated. You can bend the metal of the pedal assembly to regain the lost motion, but it'll just bend again if the throttle cable or carb linkage is stiff. Best to weld-in a reinforcement after verifying that there's no excess force required at the cable or carb(s).

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Old 08-09-2022, 11:02 AM
tjs72lemans tjs72lemans is offline
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First off, I have the power seat back locks with solenoids. They continue clicking with door open, so trying to hear solenoid at tranny from above won't work. I could tape the switch as if pressing accelerator pedal and crawl under car to hear.
I do have that type of pedal solenoid Shurkey. I read the manual and I thought it said push forward (there is just a bit of the bar sticking out to push maybe 1/8" and done). Sounds like you're say the opposite. Maybe I understood the manual wrong.
Does this switch kick down just from 3rd to second or second to first also?
Yes, I do have power to switch. My next step was to check if power was going through switch, but didn't know where to check that. That was why I asked about where that solenoid was on tranny. I see two electrical connections there as posted.

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Old 08-09-2022, 07:16 PM
Schurkey Schurkey is offline
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Quote:
Originally Posted by tjs72lemans View Post
I have the power seat back locks with solenoids. They continue clicking with door open, so trying to hear solenoid at tranny from above won't work. I could tape the switch as if pressing accelerator pedal and crawl under car to hear.
Seatback solenoids and trans solenoids are probably on different fuses. Pull the fuse for the seatback solenoids so you can hear the trans solenoid.

You can't "tape" the switch and have it do any good--it'll click once each time it's activated.

Or just get in the car, shut the door, open the windows, and stab the gas pedal with the ignition "on" but not running. Don't flood the engine.

Quote:
Originally Posted by tjs72lemans View Post
I do have that type of pedal solenoid Shurkey. I read the manual and I thought it said push forward (there is just a bit of the bar sticking out to push maybe 1/8" and done). Sounds like you're say the opposite. Maybe I understood the manual wrong.
Likely. The switch has to be pushed AGAINST the direction of the gas pedal, so that the initial position is set. Then the pedal levers the switch arm forward, the ratchet action sets appropriate adjustment.

On rare cases, the ratchet mechanism gets worn-out. The ratchet action is provided by a copper contact moving along a ridged plastic "shoe". The plastic ridges can erode.



Quote:
Originally Posted by tjs72lemans View Post
Does this switch kick down just from 3rd to second or second to first also?
Should drop to first if vehicle speed is low enough.

Quote:
Originally Posted by tjs72lemans View Post
Yes, I do have power to switch. My next step was to check if power was going through switch, but didn't know where to check that.
Check the OTHER terminal on that same switch. Your test light will light/not light/light/not light as the switch is activated and released, provided the switch works--contacts inside aren't burned. But don't screw-up the adjustment as you're moving the switch arm, or you'll have to start over with setting the initial position by moving the switch arm fully rearward, then matting the gas pedal.

Quote:
Originally Posted by tjs72lemans View Post
That was why I asked about where that solenoid was on tranny. I see two electrical connections there as posted.
Yeah, I can never remember which is which, either.

The second blade on that trans connector is either for the switch-pitch torque converter solenoid ('65--'67) or for the TCS (later than '67, if equipped.)

The two blades form a "T". The vertical leg of the "T" is for the kickdown.
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Last edited by Schurkey; 08-09-2022 at 07:28 PM.
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Old 08-09-2022, 09:34 PM
tjs72lemans tjs72lemans is offline
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Thanks Shurkey. After I posted and thought of my idea of taping the switch, I figured it was just a one time click I'd be missing and that wouldn't work. When I tested the wiring to accelerator switch while disconnected, I found it had power. Not sure how I get on the switch with it connected to see if power is going through. Other than listening for solenoid click or if I can find power on tranny side wiring to switch. Since I don't know which of two tranny wires is for solenoid, I'll check both.
Here is what the manual says on resetting the switch. It sounds opposite of what you say, unless I'm interpreting it wrong.
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Old 08-09-2022, 09:58 PM
Schurkey Schurkey is offline
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I think that manual illustration is backwards. Try it my way, see if the system comes back to life.

If you don't want to check for power, you could disconnect the two-wire harness and then connect an ohmmeter across the two switch terminals. Open circuit at rest, near-zero resistance when the switch post is pushed forward by accelerator pedal (or your finger.)

The switch should engage BEFORE WFO, like at 2/3 or 3/4 throttle. If you push it too far, you'll mess up the adjustment and have to start over.

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Old 08-11-2022, 12:36 PM
tjs72lemans tjs72lemans is offline
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Here's what I found. It looks like the switch is good. My ohm reading is 1 at rest and goes down (around 0) as it is depressed. Taped switch as if depressing and with ignition on (before start and gauges lit). Underneath with test light and one end grounded, I checked both wires to solenoid and other TCS? and no power on wires. Not sure how the switch works, but I assume with taped to activate, it should send power to wire to solenoid for the one time click. Or is the wire only powered at the depress mode for an instant and sending signal to solenoid?

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Old 08-11-2022, 01:29 PM
tjs72lemans tjs72lemans is offline
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Update. I went out and using my test light to check power out of switch. It works. My test light shows power comes out only when switch is about 1/8" away from full depression as if floored. So, I made sure my switch was taped at full depression and I have power to wire underneath at first of the two solenoids on tranny. Now I know the front receptacle is the solenoid for kickdown. I also have full throttle and switch is fully depressed. I don't feel much of the ratcheting as described earlier, maybe due to wear. I assume this is only useful for the adjustment if you want kickdown at partial throttle rather than only full throttle? As my pic shows, this is at rest when pulled back as manual describes. But, I assume there is no setting it if the ratchet catch doesn't work?
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Old 08-11-2022, 01:50 PM
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The connector on the switch at the gas pedal has two wires. One of the wires has power with the key on. Power goes through the switch when activated and out the other wire to the transmission. You can disconnect the connector at the gas pedal and jump it with the key on and listen for the solenoid to click in the transmission. This will verify the solenoid is working. This will also help you verify which wire is the one for the solenoid at the transmission.
If you want to test the switch, plug the connector back in and put a test light or meter on the wire that has no power and activate the switch. Hope that makes sense..

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Old 08-11-2022, 02:35 PM
Schurkey Schurkey is offline
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Quote:
Originally Posted by tjs72lemans View Post
My ohm reading is 1 at rest and goes down (around 0) as it is depressed.
"Around 0" when activated is good. "1 at rest" is not. Do you have your meter on the correct (low-ohms) scale? At rest, the meter reading should be "open circuit", "infinite", or "out of range". "1 ohm" makes no sense, 1 megohm might.

Quote:
Originally Posted by tjs72lemans View Post
I assume with taped to activate, it should send power to wire to solenoid for the one time click. Or is the wire only powered at the depress mode for an instant and sending signal to solenoid?
The solenoid clicks once, but the power to it is constant as long as the gas pedal is pushed far enough to activate the switch.

Quote:
Originally Posted by tjs72lemans View Post
I went out and using my test light to check power out of switch. It works. My test light shows power comes out only when switch is about 1/8" away from full depression as if floored. So, I made sure my switch was taped at full depression and I have power to wire underneath at first of the two solenoids on tranny.
Seems reasonable. Still not sure of your switch adjustment.

Quote:
Originally Posted by tjs72lemans View Post
Now I know the front receptacle is the solenoid for kickdown.
I wouldn't call it the "front receptacle". It's the vertical leg of the "T" made by the two blades on the trans connector.

Quote:
Originally Posted by tjs72lemans View Post
I also have full throttle and switch is fully depressed. I don't feel much of the ratcheting as described earlier, maybe due to wear.
The only time it ratchets is to set the adjustment. After that, no ratchet until you set initial position again.

Quote:
Originally Posted by tjs72lemans View Post
I assume this is only useful for the adjustment if you want kickdown at partial throttle rather than only full throttle?
The switch cannot be adjusted for part-throttle shifts. That is, you can set it most anywhere you want...but the first time you fully depress the throttle, it's going to ratchet into proper position where it kicks-down at "near" full-throttle.

Quote:
Originally Posted by tjs72lemans View Post
As my pic shows, this is at rest when pulled back as manual describes. But, I assume there is no setting it if the ratchet catch doesn't work?
The photo is not helping me visualize what's happening. Blurry, sideways, doesn't show the gas pedal rod vs. the post on the switch.

If the ratchet is worn-out, the switch will not hold adjustment. That's possible, but rare.

Leave the gas pedal in the idle position. Depress the lil' lock-tab on the switch plunger, and move the plunger OPPOSITE the direction that the gas pedal rod moves the post/switch plunger. I bet you'll hear and feel the ratchet.

When the post on the side of the plunger is closer to the gas pedal rod, cram the pedal to the carpet. You'll again hear the switch ratchet into position. The switch has self-adjusted to correct position.

Done.
[Edit] Found a photo of the pedal vs. switch; I was mistaken. The switch moves opposite the way I thought it did. The service manual illustration you posted is correct--but--are you depressing the lock-tab to move the plunger FULLY to the end of it's travel? Then mat the gas pedal, you should hear it ratchet.
[/Edit]
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Old 08-11-2022, 05:49 PM
tjs72lemans tjs72lemans is offline
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The manual doesn't say anything about depressing a lock tab. Is this something that gets bent and can be bent back it to catch? I don't understand the set reason if I mash the pedal to the floor and the switch activates power.

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Old 08-11-2022, 06:07 PM
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Quote:
Originally Posted by tjs72lemans View Post
The manual doesn't say anything about depressing a lock tab.
Does it work properly when you follow the manual instructions?

Quote:
Originally Posted by tjs72lemans View Post
Is this something that gets bent and can be bent back it to catch?
Don't bend it so far that it takes a permanent deformation. Flex it down enough to clear the metal it normally catches on, when the switch is adjusted, the lock tab pops back up and works as it should.

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Old 08-11-2022, 08:06 PM
tjs72lemans tjs72lemans is offline
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I did try to pull the plastic bar out and make the spring metal protrude a bit. It held the bar out at about 1/4" after that. When floored and released it went back to where it always has been (about 1/8" sticking out from housing). I still don't understand the reason for the initial setting if it only works when floored and bar is pushed all the way to the rear with pedal rod (which does activate the power). I still haven't tested to see if my solenoid clicks yet. I do have power down to the wire for the solenoid to activate. Or as I look at your earlier post pic, is the one tab supposed to be sticking out enough so that it catches the housing on that tab and doesn't go into it any farther?

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Old 08-12-2022, 12:58 AM
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Let's see if we can't simplify things. The kickdown switch is auto adjusting once you push the tan plastic rectangle piece forward as far as it will go towards the firewall. It should go to its forward most position and you might hear ratcheting as you push it. Then you push the accelerator to the floor and the throttle arm is going to contact the plastic pin sticking out of the switch and move the tan rectangle piece back in the holder. At this point things are adjusted and you should have power going through the switch when you test pushing the pedal all the way to the floor. Even if you mildly push the accelerator to the floor it will adjust for testing, and the next time you really mash the pedal it will probably self adjust just a bit more.

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Old 08-12-2022, 02:37 PM
tjs72lemans tjs72lemans is offline
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Today's update. I taped the kickdown switch to replicate full throttle. Key on. Under car with test light on solenoid wire and power to wire. Jumper wire on solenoid. Touched solenoid wire with power to solenoid jumper wire and no click. Some small spark so I know it is getting power. So, it looks like my solenoid worked one time for me since I restored car and quit. I will assume when I had the tranny rebuilt, they don't replace something like this with new? Just rebuild the internals? The solenoid really doesn't look too dirty on outside white plastic, But, it would be odd to work once and burn out.
Now my question is, how to replace? Does this just pry out? Does pan have to come off and go from inside? I'm not familiar with auto trannys.

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Old 08-12-2022, 03:20 PM
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The white plastic is just a plug with terminals. The actual solenoid has a wire that connects to the inside of this terminal plug.

If you have a two terminal plug, the rebuilders may have connected the solenoid wire to the wrong terminal.

You need to drop the pan to check this
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Old 08-12-2022, 07:55 PM
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Thank you for the pics. I did call the rebuilder and he said he puts power to them and if they click, he leaves them. If bad, he replaces. Unfortunately, mine worked one time after rebuild. Dang!
Looks like I have to drop the pan and loose my new fluid. I wish I had a drain plug to save.
It does only have one spade for one wire.
I may as well replace the filter while I'm in there, even though it only has 1500 miles on it.
He did say something about the gasket doesn't need to be used. But, he also said something about if the new part isn't the same as the old. So, I hope that is self explanatory when I get to that point.

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