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Thread: 450 Transmission noise becoming unbearable

  1. #61
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    Quote Originally Posted by reinaldo_is_spam View Post
    if you're being serious , that'll come back to bite you
    A retired chief engineer visited my workshop yesterday. I suspect he dropped the gearwheel into my box.
    Drives a Smart Cdi - 65 to 85 MPG

  2. #62
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    ........................................
    Last edited by Mjolinor; 28-09-2017 at 07:08 AM.

  3. #63
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    The Smart 450 transmission employs the very common Borg-Warner synchromesh units:



    This synchromesh unit has no built in detent to hold shift sleeve in engagement or in neutral position.

    Note also that the ridge on each strut key does not centre shift sleeve in its middle neutral position. Rapid wear of synchroniser rings (called blocker ring in the video and also called baulk ring) would result if shift sleeve were not centred in neutral position. Centring is done by shift drum grooves and detents.

    When working on my transmission I had it sitting as shown in the photos on the workbench with the shafts orientated vertically. With both shift drum and selector fork assembly removed I checked out operation of the shift sleeves. Gravity was enough for shift sleeves to drop out of engagement with gears. This obviously only applied when lifting shift sleeve vertically to engage a gear. Gravity would of course keep shift sleeve engaged if moved downwards.

    Conclusion:
    The detents in shift drum prevent shift drum from rotating and keeps shift sleeves locked in either their engaged or neutral positions.
    Last edited by tolsen; 28-09-2017 at 08:20 AM.
    Drives a Smart Cdi - 65 to 85 MPG

  4. #64
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    The 451 gearbox also falls out of gear when vertical. It is one of the strangest gearboxes I have ever seen, the 450 is a lot more normal I think.

  5. #65
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    Transmission went in in just a few minutes. Worst is fitting the EGR valve and its support bracket. With the EGR valve deleted, access would be greatly improved.
    Filtered the old transmission oil and filled up transmission. Went for a test drive. No unbearable noise no more and all gears work including reverse.
    Wonder how much I saved by doing the job myself. Perhaps as much as one grand?
    Drives a Smart Cdi - 65 to 85 MPG

  6. #66
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    The saving depends very much on how you value your time subtracted from the cost of learning something new. In Scotland learning is free but not so in England.
    .

  7. #67
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    Quote Originally Posted by Mjolinor View Post
    The saving depends very much on how you value your time subtracted from the cost of learning something new. In Scotland learning is free but not so in England.
    .
    What has learning got to do with it? You think this is the first time I've worked on a Smart?

    Anyway Smart is now happy all screws and parts were correctly fitted, torqued up and secure with no mishaps underway or broken parts

    We will now go catch fish. Maybe crabs, scallops or lobster. Have not dared hauling my trailer due to the unbearable noise so unable to transport my large boat.
    Drives a Smart Cdi - 65 to 85 MPG

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