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Thread: 451 diesel gearbox update

  1. #1
    Join Date
    Mar 2012
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    Burnley
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    451 diesel gearbox update

    I bought myself a 2009 CDI with a gearbox fault. The fault is that the 135 drum works fine but the 24R does not.

    Sometimes it is fine then a bang and I only have 1, 3 and 5. The ECU is not up to date as far as I know (Screenshot attached) but can anyone tell me if this is the fault that is fixed by the update.

    Looking at the gearbox I would guess that the locking pins that are supposed to prevent the drum rotating on its own are not locking into place properly sometimes.

    smart.jpg

  2. #2
    Join Date
    Dec 2004
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    Sounds more like a mechanical fault than a software one. Software usually shows up 3 lines & flashing gear indicators before loss of gears.

  3. #3
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    It does that too. flashing gear indicator and spanners.

  4. #4
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    Then I'd get the update done & go from there! Don't let MB fob you off with it needs a new transmission before they run the update though, diagnostics does say that but they can ignore & run update 1st!

  5. #5
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    Cheers for that.

    I did think about taking the shift motors off and checking them, some of the pictures on the net show those motors in a terrible state.

    Have you any experience of that, is it likely to improve anything?

  6. #6
    Join Date
    Jan 2011
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    uk
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    Quote Originally Posted by Mjolinor View Post
    Cheers for that.

    I did think about taking the shift motors off and checking them, some of the pictures on the net show those motors in a terrible state.

    Have you any experience of that, is it likely to improve anything?
    Are the motor's identical..?...............

    If so I have a cunning plan I'm sure you can think of too.......
    You're so money supermarket and you don't even know it!

  7. #7
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    As far as I can tell the motors are identical but I haven't got them off. Remember this is a Smart car so at least five other thigns have to come off before you get to the bit you actually need to remove.

    I got the fan off the intercooler after removing some pipes and other bits from the air box and the EGR valve but haven't worked out yet how to get the intercooler / air scoop off.

    Not as many how tos for the 451 as I would like and the amount of space inside the engine cover on the CDI makes the 450 look as roomy as a Morris Minor.

  8. #8
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    OK, Got the intercooler out eventually which gave me access to the gear change mechanisms on the top of hte gearbox. Removed those and check the motors, the 24R is slightly noisier than the 135 but nothing wrong with either of them. I took the motors off and stripped them, commutators and brushes are good so I stuck it back together.

    Looking in the hole it came out of the two gears on the selector drums, the 135 drum is nice and tight with maybe 45 degrees of play, the 24R drum will turn a full half turn. At the end of the travel you can see the fork starting to move but at the other end of travel it doesn't and you can feel the pin slip out of the slot or at least that is what I imagine is happening.

    I think it is a gearbox job because even if I get it apart I will not be able to buy internals form Merc I don't think so ebay to the rescue if I can get a good deal.

  9. #9
    Join Date
    Nov 2007
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    3,392
    Perhaps broken roll pin or something simple for one of the forks? Only way to find out is open out.
    Drives a Smart Cdi - 65 to 85 MPG

  10. #10
    Join Date
    Mar 2012
    Location
    Burnley
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    Got a gearbox, 2010, "low mileage" whatever that means, 100 + 40 delivery. Happy with that.

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