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Thread: K1 / K2 spring kit

  1. #1
    Member Hakie's Avatar
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    K1 / K2 spring kit

    A few weeks ago i changed oil and filter of an automatic transmission from a friends W126. He had troubles with hard shift and slipping gear. For that reason we also replaced the K1 and K2 springs. He ordered the parts as i have no experiance with this K1 and K2 spring kits!
    It turned out to be a major improvement for the transmission. It shifts very smooth now, almost perfect.

    When i am going to change oil and filter for the E500 and 400E i want to replace the springs also and hope to get an improvement in shift too. Also as a "while i am in there" thing.

    What i know about the spring kit is:

    The K1 spring kit (new type) is universal and has partnumber A126 270 4477
    That should fit in our transmissions?

    The K2 spring kit has multiple partnumbers: A126 270 xx35
    Witch one should i order for our transmissions?

    I searched the forum for this subject but could not find anything pointing to this partnumbers?

    The costs of the kit's ordered at the dealer are under $10 each, so that is why i think it is worth it to replace them?


    IMG_2225.JPGIMG_2226.JPG

    From Gsxr's site:

    IMG_2223.JPG

  2. #2
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    Re: K1 / K2 spring kit

    There have been some changes to the springs through the years. Some of those springs were in a TSB on our ng, some are for 722.4xx, and some address specific issues. The K2 is the example there.

    There is a superior shift kit available for ~ $45. It has several options for making the shifts firmer or softer.

    Those kits are the accumulator kits. I went through last year and ordered every one available and experimented. No notes in my hand- but I believe for most(unless you have a broken spring), that you can replace the K2(effecting 2-->3 shift) and move the old K2 into the K1 position. Monkeying with the shift kit plan on removing and changing springs 2 or 3 times. K1 and K2 are on either ends of the same spool. So changing one effects the other...

    You can turn up the pressure slightly which will quicken shifting. Clean fluid will improve shifting.

    Is it worth replacing them? If you are not experiencing a problem- don't touch it. If you want to improve something- please give us more details on how it is shifting.


    I've got a 1992 first gear start valve body built with improvements, just hasn't been tested yet.

    Michael
    Last edited by samiam44; 1 Week Ago at 05:06 PM.

  3. #3
    Member Hakie's Avatar
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    K1 / K2 spring kit

    Quote Originally Posted by samiam44 View Post

    There is a superior shift kit available for ~ $45.....

    Is it worth replacing them? If you are not experiencing a problem- don't touch it. If you want to improve something- please give us more details on how it is shifting.

    Michael
    Thanks Michael,

    I have 3 cars with automatic transmission. All of them shift ok, but can be improved because the shifts 2-3 3-4 can be "firm". Not really something to worry about but when this can be fixed with new K1 and K2 springs, why not do that? It dont costs much.
    I read about the superior kit but thought of keeping the partnumbers original Mercedes.
    After replacing them in the W126 the other day i was surprised of the effect. Better than only an oil and filter change.
    Is it not so that the springs wear out a little after so many years and replacement is a good thing?
    My thought was to change the springs as a job while i am in there. There must be a valid K2 mercedes partnumber for 400/500 transmissions?
    Changing the springs only still is a time consuming job so i prefer not to experiment with that. When i am not sure about the right parts i will leave it alone.
    Last edited by Hakie; 6 Days Ago at 11:13 PM.

  4. #4
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    Re: K1 / K2 spring kit

    I have the superior Shift Kit installed in my 560SEC and also in my 300CE and it greatly improved the shifts and got rid of the occasional flaring on the 300CE.

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    Re: K1 / K2 spring kit

    I ordered a month ago a sring ‘kit’ made of 21 or 22 springs for my 92 500E but I don’t remember what was it called exactly?


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    Re: K1 / K2 spring kit

    The K1 factory spring upgrade (126-270-44-77) will slightly firm up the 2-3 upshift. You only want to do this if the 1-2 and 3-4 shifts are normal, but 2-3 is soft or flaring. Also, it's possible a previous owner may have already installed this, can't tell until you remove the old one and measure the wire diameter on the springs (they are 0.1-0.2mm thicker on the new springs). I'm not aware of any factory spring upgrade for the K2, which affects the 3-4 upshift.

    The Superior kit allows going even firmer beyond what the 126-270-44-77 will do, along with parts to adjust other shifts. Again, unless you are having shift issues, I wouldn't mess with anything. Pics of the Superior kit, and their instruction sheet, are here:
    http://124performance.com/images/W12...erior_springs/

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  10. #7
    Senior Member Eno's Avatar
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    Re: K1 / K2 spring kit

    Where can one buy the so called Superior Kits?
    Are they after all market?
    Does MB produce such Superior Kits?


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    Re: K1 / K2 spring kit

    The Superior (brand name) kit is available from various vendors in the USA, including sellers on eBay. Here's a couple links:

    https://www.google.com/search?q=superior+K722A-G

    https://www.google.com/search?q=supe...=lnms&tbm=shop

    Links above are for the 722 kit for gas engines. There is a different kit for diesels.


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    Re: K1 / K2 spring kit

    https://superiortransmission.com/pro...erior-k722a-d/

    The last one I ordered on ebay for $85 shipped. The one before also from ebay for $65 shipped.

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    K1 / K2 spring kit

    After contact with the owner of the W126, these are the 2 mercedes partnumbers we build in the transmission. I will order the 2 and decide when i change fluid and filter If i replace the spring kit's. I think he payed only 12-14 dollar for the 2 kits.
    Thanks for all the input so far!

    IMG_2227.JPG

    Found some extra info of the K2 kit:

    https://www.ecstuning.com/b-genuine-...it/1262700535/
    Last edited by Hakie; 6 Days Ago at 01:00 PM.

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    Re: K1 / K2 spring kit

    Hakie,

    Maybe you need to lower the line pressure slightly if all your shifts are too firm? As a rule, springs don't settle if made properly. Manytimes, you will find a broken spring where a rust pit had started and it failed with fatigue cycling. You can read the superior's information, but I know it has several springs for each K1 and K2. I think you can go softer, firm or extra firm. MB kits are nice between the color coordination and you get new seals.

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    Re: K1 / K2 spring kit

    Quote Originally Posted by samiam44 View Post
    Uou can read the superior's information, but I know it has several springs for each K1 and K2. I think you can go softer, firm or extra firm.
    IIRC, Superior only offers firmer-than-stock for K1 (2-3) and K2 (3-4) upshifts, and only offers a softer-than-stock modification for the 1-2 upshift.

    If you are picky about shift quality, it can take a lot of trial and error experimentation, with 1-2 hours labor each time to drop the pan and/or valvebody (if necessary). Not fun!


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  21. #13
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    Re: K1 / K2 spring kit

    Quote Originally Posted by samiam44 View Post
    Hakie,

    Maybe you need to lower the line pressure slightly if all your shifts are too firm? As a rule, springs don't settle if made properly. Manytimes, you will find a broken spring where a rust pit...
    Yes Michael, i think the best thing to do is inspect the springs first and than decide what to do. It is not a big problem in my case. Also it is a bit complicated for me to explain the situation. I find therms as "hard, harsh and firm" shifts.
    Maybe i just have to live with it. The cars are all 20+ years old and that comes with some wear in the trans.
    Also the oil and filter change can change the feel of shifting. The cars are in winter season soon. In that period i will do de transmission maintenance.

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    Re: K1 / K2 spring kit

    The type of ATF can change shift quality... in general, fully-synthetic can provide slightly more consistent shifts between cold and hot. If you change from a Dexron-III spec (7.5 viscosity) to a Dexron-VI spec (6.0 viscosity) you may need to adjust the vac modulator, and/or possibly fiddle with some springs. I prefer to use the fluid spec the 722.3/4/5/6 was originally designed for (7.5 cSt) but that's just me. There's been discussion / debate about this in other forum threads.

    Also, if ALL the shifts are too firm or too soft, this can be adjusted via the vacuum modulator. If the vacuum modulator is original or old, it is not a bad idea to replace it, I had some intermittent odd shifting (flaring, IIRC) on one transmission which was cured with a new modulator.


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    Re: K1 / K2 spring kit

    If you get clever you can firm them ALL up...I don't have my notes in front of me but b/w doubling up on springs, seeing what can be made to fit where you can build one AGGRESSIVE valve body.

    ...it makes for a good time
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    Re: K1 / K2 spring kit

    Quote Originally Posted by gsxr View Post
    The K1 factory spring upgrade (126-270-44-77) will slightly firm up the 2-3 upshift. You only want to do this if the 1-2 and 3-4 shifts are normal, but 2-3 is soft or flaring.
    Very important note! Please do consider this.
    Normally its used because 2-3 upshift ist the most used shift on these boxes and it wears out at first (besides the reverse). So its starts to get super soft (and long) and then flares.
    On my gearbox i did this spring update preemptively without knowing the gearbox, nor driven it. The result is that all shifts are good, but the 2-3 is veeeery quick and clearly noticable. I played around alot with the modulating pressue which adjusts shift speed and softness for all gearshifts, but when i do the pressur so that 2-3 shift is perfect, all other shifts are tooo soft and take to long (almost flare).
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    Re: K1 / K2 spring kit

    Quote Originally Posted by Christian_K View Post
    On my gearbox i did this spring update preemptively without knowing the gearbox, nor driven it. The result is that all shifts are good, but the 2-3 is veeeery quick and clearly noticable. I played around alot with the modulating pressue which adjusts shift speed and softness for all gearshifts, but when i do the pressur so that 2-3 shift is perfect, all other shifts are tooo soft and take to long (almost flare).
    So you mean, if I want to swap a transmission, I shouldn't do it? As it's what I'm just intended to do.
    Never driven the trans, should be just fine. 600SEC though. And my car isn't stock either. (510hp)
    Okay, maybe, I'll get a fluid flush and we'll see how it goes. Also I really want the 1st gear start badly.

    Anyway, I stongly recommend anyone to use Dexron-II in the gearbox. DxIII is way weaker and burns clutches. DxII makes shifts quick and stable, although feels strange when cold.
    I'm looking forward pouring Redline Type-F ATF with 10cct viscosity index.
    Last edited by whatever; 14 Hours Ago at 03:18 AM.

  28. #18
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    Re: K1 / K2 spring kit

    Whatever?

    "Anyway, I stongly recommend anyone to use Dexron-II in the gearbox. DxIII is way weaker and burns clutches. DxII makes shifts quick and stable, although feels strange when cold.
    I'm looking forward pouring Redline Type-F ATF with 10cct viscosity index. "

    What brand are you purchasing D2 fluid? I don't understand what you mean when you say a fluid is "weaker and burns clutches". Is the viscosity lower?

    I'm running redline in mine now- shifts are fine. Quick and crisp with the v/b changes. But it was a lot of work. For most, I bet they can do a shift kit/new flluid and then play with modulator pressure a bit and be happy- if the transmission is healthy. Type F fluid has [no] friction modifiers and seems to help if you have glazed some discs. It may help, but you should start saving coins for a rebuild.

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