Auto Trans, no kickdown and rough shifts

[Iconic]

OK, I've been living with this for quite a while (since I got the car).
It has now risen to the top of my "list".
I have a couple of drives coming up, so I would love to get this corrected.
I've read a lot of the MB repair manual, our Tech Manual, and our Forum posts.
I have not been able to put the answer to the puzzle together.
Maybe you can help?

Here are the clues:
While driving (the problem):
I have no kickdown of the trans when I am driving the car and I floor the accelerator pedal.
If I floor it from a stop with the selector in "4", the car takes off in 2, not 1 as it should.
The shifting is harsh always.
If I accelerate briskly in any gear, but not to the kickdown switch, the car NEVER downshifts by itself.
Otherwise the trans works. I get all 4 gears at reasonable shift points. I can move the selector to "2", and the car starts in "1" (and then burns rubber into 2nd, I love that    )

Engine off, ignition on (the clues):
If I move the throttle pedal off the idle position, I feel a click in the 3 position solenoid on the trans. (that means my idle switch works, correct?)
If I engage the kickdown switch with the throttle pedal, I either don't feel anything, or maybe something very faint.
But, when I lift off the kickdown switch, if do feel a click in the 3 position solenoid.
The 3 position solenoid is still connected to the trans. I cannot move it with my hand (engine off or on, in any scenario). Should I be able to move it with my hand?

Engine on, but not driving (more clues):
My CSS (constant speed solenoid) functions perfectly (it engages when I move from Neutral to 4 and when I move to Reverse, it disengages when I move back to Neutral. (doesn't this mean the pressure sensors on the trans work?)

I know all of this means a lot of the system is working ... but I don't know what to try next.
Does the 3 postiion solenoid get stuck, or does the thing in interfaces with on the trans get stuck

Who can help with this puzzle??? It would not be easy for me to start checking pressures. I'm hoping with the clues we can figure out what works and what doesn't.
THANK YOU.

[Larry & Norma]

You should remove the inspection plate on the transmission tunnel (passenger side on a left hand drive car)
then you can see the solenoid in action or not as the case may be!
Hope your carpet is not glued down on the tunnel.

[twistedtree]

Larry is right, you need to remove the inspection plate to gain access.  But you say the solenoid isn't moving, so I'm guessing you already have it removed?

Here's the first set of checks:

1) Ignition off, grab the solenoid rod.  It should naturally be in its center position.  You should be able to move it forward against spring pressure, and move it aft against spring pressure, and it should spring back to the center position.  This will confirm proper physical movement.  If it doesn't work, solve this problem first.  The solenoid could be seized, or the level into the trans could be seized.

2) Ignition on, engine off (do yourself a favor and remove the fuel pump fuse while you do this).  A little gymnastics are required for this.  With the gas peddle in its mid position, the solenoid should be in that centered position, and you should be able to manually move it to the forward and aft positions, and it should spring back to center just like when the ignition was off.

3) With the gas peddle at idle, then solenoid should be firmly forward (or I could have this backwards and it should be aft).  If this doesn't happen, check the throttle body switch adjustment and operation.

4) With the gas peddle on the floor, the solenoid should be hard aft.  (again, I could have this backwards and it should be forward).  If not, then check the kick-down switch on the firewall floor behind the gas peddle.

5) If all the above is working, then you need to rig up a pressure gauge and confirm that you have the correct pressures in each of the three solenoid positions.  I'd have to go back and check the BBB to remind myself what the correct pressures are, but 5, 15, and 30 psi stick in my mind.  Adjusting the linkage between the solenoid and trans can correct any issues.  It's also possible that the solenoid has lost its umph and can't shift firmly enough, in which case it needs to be replaced.

[Iconic]

Peter,
Thank you. Yes, you are correct, I had the inspection cover off. That is how I know when the solenoid "clicks". I can actually feel the click-vibration in the rod and solenoid with my hand on the solenoid and rod. The solenoid is not moving the rod more that a few thousandths of an inch when I feel it "click".
Ok, so my writeup was not clear.

In your #1, ignition off scenario, how much should the rod move? I can move it a few thousandths of an inch. That is it.
How hard is it to move? Should I be able to easily move it with my hand? I suspect the answer is yes.
So, my solenoid is seized
Do I disconnect the rod and see which is seized, the solenoid or the lever into the trans?
Or, is it usually the solenoid that seizes?

What technique do I use to free it up?

(Yes, when doing all of my checks so far, I had the #4 Fuel Pump fuse removed.)

Since I could feel the vibration/click in the solenoid when I moved the pedal and when I floored the pedal, I figured the idle position switch and the kickdown switch and all associated wiring was good ....and I am probably correct.

Now, How do I free up the seized solenoid (I did spray a bunch of penetrating oil on it)?

[twistedtree]

It should move more than that, so you have found a fundamental problem.

Beware - I've messed with one of these exactly once, so pay less attention to me than some of the guys here with real experience if they chime in.....

Yes, start by disconnecting the rod and working the two parts independently.  If I recall correctly, the trans lever will move freely in one direction, and against spring force in the other, with the mid point being right where the spring force begins.  And the solenoid is the same, but opposite, with the spring acting in the other direction.  I also recall that significantly more force is required in one direction that the other, but I don't recall which.  Regardless, is should move by hand - no tools or levers required.  Later this AM I can go check on one that I have on the shelf.

If the trans lever is sticking I'd just hit it with PB Blaster and gently work it with pliers or such.  If it's the solenoid, I'd try to remove it and do the work on the bench.

By the way, I remember reading here about someone who had a solenoid that was confirmed to be working and shifting properly, but it turned out that it didn't have enough umph to really do the job properly.  Replacement solved the problem.

On the other hand, I found the rod adjustment to be quite sensitive on the car I worked on.  I adjusted it with the engine off per the tech manual, but with a pressure gauge attached and the engine on, I was not getting the correct pressures.  More fiddling with the rod adjustment solved it.  There are two morals to the story:

First, even once you get the thing working, you may not be done and might still need to do the pressure test/adjust

Second, it's conceivable to me that the improvement yielded by replacing an old solenoid actually came from the consequential rod adjustment, not the solenoid itself.  This is just a theory, but it reinforces the importance of checking with a gauge if you are still having trouble after freeing everything up.

On one of my cars I found the rod to be grossly missadjusted and pegged up against one extreme.  Some previously working on the car didn't know what they were doing.  Proper adjustment completely solved the problem.  In your case, the lack of kick-down suggests that the high pressure position is never being achieved, and the harsh shifts suggests the low pressure position is not happening either.  The conclusion would be that the lever is stuck in the mid position, which is what you might expect on a car that sat for a long time, as many of ours have.  By the way, if this is the case, your up-shifts while accelerating normally should be fine, but downshifts as you glide or brake to a stop should be rough.  It's those glide-to-a-stop downshifts where the throttle switch activates and shifts the trans to low pressure which softens the down shifts.

[twistedtree]

I checked the trans on my shelf.  Shifting the rod forward goes against the spring in the solenoid, and is the lighter of the springs.  Shifting aft is against the trans spring and is the harder of the springs.  Regardless, both should be movable by hand.

Let us know how you make out.

[twistedtree]

Oh, and the rod moves around 3/8" to 1/2" in each direction as measured at the ball joint.  That distance is just eyeballing it, but it's pretty close.  It's not a few thousandths as you are seeing.

[Iconic]

Peter,
Thank you again.
I now understand things better and I know what I need to do next (hopefully this weekend).

Can you, or anyone, tell me if I can remove the 3 Position Solenoid through the access hole in the tunnel?
I'll try to free it up first, but I might need to remove it.

I feel like I am finally zeroing in on an issue that I have ignored for 3 years (I had "bigger fish to fry").
Proper trans function will feel very good. 

[twistedtree]

Can you, or anyone, tell me if I can remove the 3 Position Solenoid through the access hole in the tunnel?
I'll try to free it up first, but I might need to remove it.

Have you confirmed it's the solenoid, not the trans lever that seized?  I haven't removed one before so I can't say for sure if it's removable via the hatch, but I expect it is.

[ja17]

Hello Iconic,

Most often the pivot at the modulator gets seized. Do not take anything apart yet. Spray everything down with penetrant first. Get some needle nose vise grips and grip the rod in the center. Have someone help you by working the accelerator pedal. Now exert the force on the rod in the correct direction while the accelerator pedal is worked. Exercise and lubricate the mechanism until works on its own. No dis-assembly required in most cases.
Good luck!

[Iconic]

Thanks Joe !!
I can't wait to give it a try.
But, it will have to wait until Sunday.

Does it help that much to have someone working the accelerator, or can I just work it with the engine off??
I soaked it over the last weekend and I gave it a 2 minute try tonight with the engine off, but no luck.

[ja17]

Be sure and spray penetrant down on the modulator end of the linkage rod. That is where the seizure happens most of the time since water also runs down to this end of the rod. A second person makes it easier. Work the linkage in both directions in sync with the person operating the pedal.

[twistedtree]

Work the linkage in both directions in sync with the person operating the pedal.

Joe, is the peddle operation recommended so you have the solenoid working with you to free up the modulator linkage?  Could it also be worked just by hand with the ignition off and no peddle movement?  Granted, you would be working against the various springs without the assistance of the solenoid, but then one person could do it.

[ja17]

You're correct Peter, one person can do it also. Eventually you will have to see it work on its own. You may want to start the car and drive it while observing it since the system voltage will be higher when the engine is running and this can make a difference.

[Iconic]

Joe, Peter, Larry, Others,
OK guys (and gals) here is where I am at.
I left the modulator linkage connected to the 3 Position solenoid and the transmission modulator.
It took quite a bit of force to get it to move the first time. I needed to use a long screwdriver pushed up against the lever for the solenoid and hit it with a hammer. This is all done through the access hole in the transmission tunnel.
Finally I got some movement. I needed to use a pliers on that same lever to move it back to the aft position.
I've worked it for about 20 minutes.
It is definitely more free. I can barely move it back and forth with my hand, but I don't get full travel and I need to use the above methods to get it to move to the ends of the travel.

The linkage is NOT springing back to the middle position on its own.
So, please tell me, are the springs that center the linkage in the solenoid or the transmission (or one of each)?
I needed a break, so I figured I would make this post.
I'm going to go and work it some more (and spray more gallons of Deep Creep) (I have no affiliation to Sea Foam Deep Creep).
One more thing: I hope I can explain what I mean here. In an axial direction, both at the solenoid and the modulator, the shafts that rotate to move the levers can move ~0.003 to ~0.008 inches freely in the axial direction. In other words they both have play with little resistance in the axial direction.
Additionally, it is no surprise to me that the solenoid, when energized, does not have enough force to move it (yet).
I don't know if those are any kind of a clues or not, or if I should just keep working it back and forth.

Added a couple of hours later:
I've worked it back and forth a bunch more, with penetrating oil.
I think I now can feel the spring in each direction from the center, but the linkage has not loosened to the point were the springs(s) will center the actuator without some help from me.
I need to give it up for today ... but, unless someone comes up with another suggestion, I will continue to work it back and forth when I can work on the car again.
Will it ever get to the point where it "springs" back to the center?
I need some encouragement.

[twistedtree]

Glad you are making progress (that's the encouragement ;-)).

But I recall a while back someone was having trouble even though the solenoid and linkage appeared to be moving properly.  They replaced the solenoid and it solved the problem, which tells me that if there is ANY drag on the mechanism, it might not work properly.  So I think you still have a long way to go.  But be happy you found a clear problem/cause of your shifting issue!

To really get things freed up, I think you are going to have to take it apart.  Have you tried disconnecting the link rod to figure out if it's the solenoid, lever arm, or both that are binding?  If the solenoid is part of the problem, I'd go ahead and remove it and work on it on the bench.  If it's binding like you say, it will probably have to be completely disassembled to get it cleaned up enough to really work properly.  And I don't even know how or if it can be disassembled.

As for the lever arm, I'll defer to others - I've never been into one before.

[Iconic]

Peter,
I'm avoiding disconnecting the linkage and removing the solenoid for 4 reasons:
1. The previous owner generally didn't mess with adjustments. They just let the car sit too long. It has been my experience, on this car, that if I find the the failure without messing up a bunch of adjustments, I'm in great shape because everything works after fixing the specific failure. Example: I've never done the throttle linkage adjustment. Once I replaced the fuel pump, distributor cap, rotor, plugs, fluids, adjusted timing, and cleaned return fuel line, the engine ran beautifully.
2. I don't really know if I can remove the linkage and 3 position solenoid through the access hole.
3. I'm following Joe's (JA17) direction where he seemed to indicate they can usually be freed up by working them until they move freely and he indicated that seizure happens at the modulator end most of the time. I'm going to try to "work" it some more ... when I have the time. 
4. I understand there are some clips or wire retainers at the ends of the linkage. I question whether I have enough room through the access hole to be able to remove the linkage.
Thanks for encouragement. 

[twistedtree]

Sounds sensible.  Keep us posted.

[Iconic]

I've made a lot of progress.
I've gone from total seizure of the linkage (needed a hammer to break it free) to driving the car and having the passing gear (kickdown) work for the first time since I've owned the car. 
This was accomplished initially by alternately striking with a hammer to move it forward and then grabbing the lever at the solenoid with a pliers to bring back down (aft). After many cycles of that (I don't know how many) it became free enough to move with the long nose vise-grip pliers on the linkage rod itself. So, by lying in the passenger footwell and grabing the linkage with a long nose vise-grip pliers (as Joe A. suggested) I was able to work it back and forth to the point where it springs back consistently from the low pressure / aft position to center. And it still hangs up in the high pressure / forward position. But, while driving it doesn't hang up at all. By the way, we are talking about me working this linkage something like 1000 cycles to get to that point. Yes, once I could move it by hand (with vise-grips) I counted in groups of 100, but lost count of how many of those. But, it was somewhere around 1000 total cycles to free it up.
The car still has rough shifts, but the kickdown does work every time now, so far (tried it 4 times last night).
Now I will look into timing and throttle linkage before I start messing with the pressure adjustment on the transmission modulator.
Thanks guys for your help. I really appreciate it.

[twistedtree]

Wow, that's great new.  My luck is never that good.

Since you now have kick-down it confirms that the forward solenoid action works.  Have you checked to see if the low pressure action works?   You could have an electrical problem if the mechanism is freed up, but the solenoid actuated movement isn happening.  It's a simple check.  With the ignition but engine not running, the solenoid should be holding the lever full aft with the gas peddle released, and it should move to the center position when you depress the peddle.  The change should be just as you crack open the gas.

It that movement isn't happening, then you can start tracing electrical issues, likely starting with the throttle switch.

[Iconic]

Lucky, yes lucky I don't have to replace the 3 position solenoid, but tell my hands how lucky I am after 1000 actuations. I spent a lot of time on it to get that lucky. 
Yes, I have full actuation to forward and aft positions with the engine off and the ignition on.
I even left the vise-grips attached to the rod so I could see it from the driver's seat and watched it while driving. (Not more dangerous than texting while driving, which I don't do.)
I get movement in both directions at the correct time (idle, medium throttle, and kickdown switch actuation) for both when the engine is off and when I am driving. It works better when driving as discussed by others, there is more voltage available when driving than when sitting with the engine off.

That brings me to a subtle question. When my Constant Speed Solenoid (CSS) kicks in, the travel is great enough to trip the throttle position switch and put the 3-position solenoid and the transmission modulator into the center, medium pressure position.
Is this correct? It doesn't seem correct to me because the CSS kicks in at idle so the engine doesn't die. And when coasting to a stop, you want low pressure in the trans (aft position) for smooth downshifts, correct? If the CSS moves the throttle linkage enough to trip the throttle position switch, then I get medium pressure and rough downshifts...... I think I know the answer, but maybe I don't.

[twistedtree]

Interesting question.  I think the throttle switch is supposed to open as soon as the throttle cracks, so that implies the CSS would have to activate the throttle switch, which would cause harsh shifts.

Have you checked to see what the BBB says?

[gvillayandre]

Hi Iconic,

I think I do have the same problem as you.

I will follow your steps on this topic.

Did you have any problem afterwards?

[ja17]

The trottle switch should send voltage to the three position solenoid at linkage idle, lowering pressure for the last downshift. When the linkage moves the switch off of idle, power to the transmission solenoid is interupted, allowing the solenoid to return to the middle (rest position) for normal driving after idle. When the linkage is pressed to kick down, the kick down switch moves the transmission solenoid to the last position.

Iconic, just be certain that the solenoid is activated forward when the linkage is at idle and returns to  middle position after slight throttle. 

[Desertpagoda]

Should anyone find themselves in need of any of these linkage or solenoid parts. I have tested, good used ones on hand. Keith 520-404-2875