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S65 722.6 gearbox issue?

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by hoppo, Sep 4, 2018.

  1. hoppo

    hoppo Member

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    Last week I was driving along and the car dropped out of gear. Still showing D but just free reving.

    Stoped restarted and all was well but a few days later it did it again. However no warning lights.

    I had the local place check and it got an implausible trans ratio code.

    Cleared the code and also rest the shift adaptations.

    Since this when ever the car shifts downnfromn4 to 3 it engages with a right thump.

    Fast forward to today and it's worse and it's giving engine management light.

    The code is 1731 gear comparison is negative or target gear not reached

    And

    0730 implausible trans ratio?

    I'm thinking it's time for a full service and new conductor plate or am I in for a much bigger bill?

    The car is a 2007 w221 s65 v12

    Thanks
     
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  2. AnthonyUK

    AnthonyUK Senior Member

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    I'm no expert by any means but these gearboxes are pretty bullet proof so I would be surprised if what you suggested didn't solve your issues.

    I hope it works out OK.
     
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  3. John Laidlaw

    John Laidlaw Senior Member

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    Nice car by the way.
    Start with a service for sure, full diagnostic (Mercedes Star, don’t know the 1731 code so I’m assuming it was a generic diagnostic), ATF change (depending on diagnostic which could be conductor plate or valve body) would be my advice for what it’s worth. Too serious and nice car to go guessing and throwing money at without an expert opinion.
    You have Mercland at Nuneaton less than 20 miles from Leicester who are well thought of
     
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  4. LostKiwi

    LostKiwi Senior Member

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    Definitely suspect the electroplate but as above if you haven't already engaged an MB specialist with Star that should be your next port of call.
     
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  5. alexanderfoti

    alexanderfoti Moderator

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    Definitely get a good independent.

    Low fluid level will cause this. Not sure I would have reset the adaptions. If there was a mechanical fault, the adaption figures may have given an indication as to which part is broken.
     
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  6. OP
    hoppo

    hoppo Member

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    Thanks for the fast response.

    I've checked the fluid level and it's all good and looks clean.

    I'll try and get it on star but I think I'll order all the bits and get them on. I understand it's a complex car but the the 722.6 is a simple transmission to work on.
     
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  7. John Laidlaw

    John Laidlaw Senior Member

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    Good point on the adaptions Alex
     
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  8. alexanderfoti

    alexanderfoti Moderator

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    It cannot hurt to change the fluid/filter/electroplate, but they normally manifest themselves with speed sensor faults as well as implausible faults. If you can get it on star, post up your adaption values.
     
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  9. alexanderfoti

    alexanderfoti Moderator

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    Guess what, mine did the same thing today.......

    Exactly the Same, hard 3/4 shift then neutral.

    Did you get anywhere with any of the suggestions. I haven't checked the level yet, and it's had a valve body and electroplate about 5000 miles ago.
     
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  10. bembo449

    bembo449 Senior Member

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    wow , Alex whats the likelihood of that happening ?o_O:confused:
     
  11. alexanderfoti

    alexanderfoti Moderator

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    Tell me about it! Although op reports hard 4 to 3 shift, mine did one hard 3-4 shift then went into neutral. Not happy on the part of the M25 with no slip road...
     
  12. Botus

    Botus Senior Member

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  13. alexanderfoti

    alexanderfoti Moderator

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    No 722.9 in these.

    I checked the level and it was a bit low @80 but not low enough to cause those issues.

    On a side note. It didn't do it again, despite me provoking it.....
     
    Last edited: Sep 10, 2018
  14. alexanderfoti

    alexanderfoti Moderator

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    Read the codes:

    p0730 the transmission has an impermissible transmission ratio. Freeze frame shows 6% engine load @3800rpm. It occurred after an overtake.....
     
  15. LostKiwi

    LostKiwi Senior Member

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    How are the clutch fill times?
     
  16. alexanderfoti

    alexanderfoti Moderator

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    Same as the last time I checked.

    K1- 4
    K2 - 7
    K3 - 7

    Interestingly, the EC tuned 722.6 tcu changed these values:

    K1- 6
    K2 - 9
    K3 - 12

    This failure happened on the EC tcu so I have swapped it back, I don't like the way it drives, it's constantly changing gear.
     
  17. OP
    hoppo

    hoppo Member

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    I've not got anywhere yet the parts just arrived so I'm hoping to get it done tomorrow or Friday.

    Fingers crossed
     
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  18. OP
    hoppo

    hoppo Member

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    So today I've replaced the conductor plate, bushing oil and filter and......

    Still got problems.

    It's better but it still downshifts very hard into 3rd. Mostly if you coast along at 40 ish the box is in 4th if you touch the accelerator it slams down into 3rd.

    I'm now getting a code for "transmition has an impermissible ratio?

    If I select any gear in manuel mode and flooring from no revs there is no slipping.

    Possible bad shift solenoid?
     
  19. alexanderfoti

    alexanderfoti Moderator

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    Mine had the same code.

    I recall somebody else having this issue. I will try and dig it up. What did the sump look like?
     
  20. OP
    hoppo

    hoppo Member

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    Fluid wasn't too bad. The magnet had the usual grey ish fine filings but no big bits or copper/brass colours.

    There wasn't much oil in or around the bushing but I guess the last thing to look at is the tcu.

    Where is the thing located in the engine bay or under the passenger floor.
     

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