Author Topic: Automatic transmission  (Read 1275 times)

Redrock2

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Automatic transmission
« on: September 18, 2021, 00:12:01 »
I need to replace the two position solenoid on top of the transmission. Is there an easier way to replace besides dropping the transmission? Thanks

wwheeler

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Re: Automatic transmission
« Reply #1 on: September 18, 2021, 03:05:16 »
Disconnect the driveshaft and lower the rear of the trans. You can sneak it out. I did not personally do that but a a friend of mine did on my W111.
Wallace
Texas
'68 280SE W111 coupe
'60 220SE W128 coupe
'70 Plymouth Roadrunner 440+6

Redrock2

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Re: Automatic transmission
« Reply #2 on: September 18, 2021, 07:50:25 »
Thanks will give it a try

WRe

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Re: Automatic transmission
« Reply #3 on: September 18, 2021, 08:10:40 »
Hi there,
are you sure you need to remove the  two position solenoid?
Often the rods and connections cause problems. You can test this without removing it by going through the opening in the tunnel. From there you can check the connections and test the  two position solenoid without them.
...WRe

Redrock2

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Re: Automatic transmission
« Reply #4 on: September 21, 2021, 14:49:54 »
Shifts are kind of a jolt. Mechanic says there is power to the solenoid but none coming out.

Pawel66

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Re: Automatic transmission
« Reply #5 on: September 21, 2021, 17:24:06 »
These rods and joints get stuck/seized very often. Have you tried to undo them and then see if there is movement? Have you tried to move them by hand?
Pawel

280SL 1970 automatic 180G Silver
W128 220SE
W121 190SL
G-class

MartinK

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Re: Automatic transmission
« Reply #6 on: September 21, 2021, 17:55:15 »
Hei, it is possible to remove the solenoid through the service hole in the tunnel without lowering the transmission. The left bolt is easier to remove if you remove the breather on top of the transmission. In most cases it is a solution only to open the linkage support which ist connected to the solenoid. unscrew the both bolts on the solenoids right hand side und remove the support. Please look with an external battery 12v DC if the solenoid really ist not working. Talk soon, Martin

Shvegel

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Re: Automatic transmission
« Reply #7 on: September 22, 2021, 01:54:05 »
I started to write a long treatise on the operation of the three position solenoid but realized it was just going to get confusing.  You almost certainly have a stuck linkage on your three position solenoid. at rest with no power applied the solenoid is in the middle position and the transmission gets the correct pressure to operate normally.  In the next position it adjusts the transmission for a low control pressure so it doesn't drag the idle down when you are stopped in gear.  In the third position it adjusts the control pressure up so the shifts are at higher RPM's and harsher.  The solenoid is powered whenever the key is on and gets it's GROUND from a couple different circuits.  Since your car is behaving like it is stuck in high pressure or "Kickdown" mode you are almost certainly dealing with stuck linkage on the right side of the transmission.  This is accessible through the cover under the carpet.  Lubricate and pry back and forth gently until it frees up.  If on the odd chance it is electrically energized which would be highly unusual it would most likely be a bad transmission kick down switch under the accelerator pedal or a frayed wire supplying a ground falsely.

wwheeler

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Re: Automatic transmission
« Reply #8 on: September 22, 2021, 15:53:10 »
If you remove the cover on the tunnel, it is easy to feel if the linkage is bound. With the solenoid deenergized, the linkage should move up and down freely. If it doesn't, it is stuck. If the solenoid is in the neutral position, it will also create harsh downshifts when you are coasting to a stop. The solenoid has to be in the low pressure (linkage going down) to have a smooth downshift. Ask me how I know!   

I have raised this point before about the solenoid not being switch by the ground but rather the positive side. On my '68 W111, it is absolutely switch by the positive. There is a diagram on this site from Sun Valley that shows that the solenoid is switched by ground. I think that is incorrect and have measured positive through the throttle switch on the Venturi. In fact I tested it last night. 

I am posting these diagrams to show the difference. The first is recognizable and the other two are ones I have found that match my wiring. Those two clearly show the trans solenoid is switched by positive and more specifically, fuse #3. It also shows that the throttle solenoid is switched by ground and that IS correct.   

Wallace
Texas
'68 280SE W111 coupe
'60 220SE W128 coupe
'70 Plymouth Roadrunner 440+6

Pawel66

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Re: Automatic transmission
« Reply #9 on: September 22, 2021, 16:12:05 »
Yes, the diagram descriptions and the diagram itself there in Sun Valley pictures are indeed incorrect. Polarity is reversed. All that is fed from controlling devices (throttle switch, kick down switch) to the 3 way solenoid is +. Ground is third screw.

I would have thought we should change it there...
Pawel

280SL 1970 automatic 180G Silver
W128 220SE
W121 190SL
G-class

Redrock2

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Re: Automatic transmission
« Reply #10 on: September 22, 2021, 22:43:18 »
Thanks for all the info. Will try and let the outcome known. Will be several weeks.

wwheeler

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Re: Automatic transmission
« Reply #11 on: September 22, 2021, 23:08:32 »
That diagram in question is in the transmission tech area and it really should be determined if it is correct or not. I say it isn't (Pawell agrees) and should be changed to a correct version. Not sure how or who determines this.
Wallace
Texas
'68 280SE W111 coupe
'60 220SE W128 coupe
'70 Plymouth Roadrunner 440+6

Garry

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Re: Automatic transmission
« Reply #12 on: September 23, 2021, 06:15:22 »
Wallace,


As a Full Member you determine what is going in the Tech. Manual. Every full member can access the Tech Manual  and add or amend the manual. There is an area to practice in before going live. We are always looking for people to add to the knowledge.




As a Group, we absolutely rely on our members adding to the manual and filling it out.


https://www.sl113.org/wiki/Main/News#HelpHowto


Garry




« Last Edit: September 23, 2021, 10:40:23 by Garry »
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Pawel66

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Re: Automatic transmission
« Reply #13 on: September 23, 2021, 09:56:09 »
I can take the drawing Wallace posted and add wire colors to it. Then I would put it in the restricted zone only. Can do it over the weekend.
Pawel

280SL 1970 automatic 180G Silver
W128 220SE
W121 190SL
G-class

wwheeler

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Re: Automatic transmission
« Reply #14 on: September 23, 2021, 15:15:25 »
Sounds like a plan. Thanks.
Wallace
Texas
'68 280SE W111 coupe
'60 220SE W128 coupe
'70 Plymouth Roadrunner 440+6

Shvegel

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Re: Automatic transmission
« Reply #15 on: September 25, 2021, 08:24:21 »
I will crawl under mine with a multimeter when I get home next week to verify what we believe to be true.

Pawel66

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Re: Automatic transmission
« Reply #16 on: September 25, 2021, 10:41:46 »
I have changed it in the Tech Manual, but please kindly check me if I did not mess up anything.
Pawel

280SL 1970 automatic 180G Silver
W128 220SE
W121 190SL
G-class

Redrock2

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Re: Automatic transmission
« Reply #17 on: November 26, 2021, 08:47:51 »
I copied replies and gave to mechanic. He was able to replace solenoid through transmission hole and did free up the rods. Transmission shifts much better but still not what I think is right. I will probably end up trailering it out of State next Spring to someone more familiar with transmission. Thanks to all who replied.

Pawel66

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Re: Automatic transmission
« Reply #18 on: November 26, 2021, 12:15:22 »
Probably now is the time to adjust modulator pressure (if you changed oil and filter). Adjust the throttle switch as well.

Adjusting modulator pressure is not that difficult (if I did it myself it cannot be difficult).
Pawel

280SL 1970 automatic 180G Silver
W128 220SE
W121 190SL
G-class

Redrock2

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Re: Automatic transmission
« Reply #19 on: November 28, 2021, 00:51:01 »
Thanks, will check that out.

Benz Dr.

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Re: Automatic transmission
« Reply #20 on: November 28, 2021, 04:37:12 »
The actual solenoid can seize up. The small lever on the end of the solenoid has a brass bushing over a pin and that's where it can stick or seize. Remove the end cover on the solenoid, remove the bushing and clean it so it will free up. This is a more common problem than you might expect.
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