Automatic car transmission

Discussion in 'DIY Marinizing' started by Duco84, Oct 9, 2017.

  1. Duco84
    Joined: Feb 2014
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    Location: Montenegro

    Duco84 Junior Member

    Has someone solved problem with shifting from D to R and vice versa, with modern automatic car transmission?
     
  2. DSR
    Joined: Mar 2017
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    Location: Michigan

    DSR Junior Member

    Hi Duco84,

    Yes, it's been done. The setups that I've seen that have had the most success has been V-drives (usually because there is enough physical room to allow for the extra length).
    Do you have a particular project you are thinking of?

    Thanks,
    Dave
     
  3. Duco84
    Joined: Feb 2014
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    Location: Montenegro

    Duco84 Junior Member

    Thank You. I'm planning to install mercedes 420CDI engine with 7G tronic automatic transmission. There is enough space in engine room.
     
  4. DSR
    Joined: Mar 2017
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    Location: Michigan

    DSR Junior Member

    Hi,

    What kind of drive setup were you planning on using it in? You do have to make sure that there isn't any thrust load on the transmission as they're not designed for a thrust load (you would need to incorporate a thrust bearing on the output shaft if there is. Also, depending on what you would be installing the engine/transmission into, typically only the 1:1 ratio is used for forward gear. No shifting and no overdrive typically.
    You will also have a lot of heat generated by the torque converter that you have to deal with. The setups I'm familiar with are the older GM hydraulic shift 2 and 3 speed automatics in a v-drive, and the torque converter is replaced with a solid drive coupling.
    What drive were you planning on using? And what kind of boat are you putting it in?
     
  5. Duco84
    Joined: Feb 2014
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    Location: Montenegro

    Duco84 Junior Member

  6. alan craig
    Joined: Jul 2012
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    Location: s.e. england

    alan craig Senior Member

    (mainly for DSR) 7G tronic gearbox has locking torque converter in all forward gears - I just looked it up.
     
  7. DSR
    Joined: Mar 2017
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    Location: Michigan

    DSR Junior Member

    Hi,

    Nice boat! I like it!

    I'm not familiar with the MB 7G tronic trans (built by ZF I believe?), but I had assumed that the converter had a lock up clutch. I also assume that with it being controlled by a TCM along with input from the ECU, that the lock up feature will unlock during situations of greater loads (higher TPS and lower manifold vacuum) so you will most likely end up having the TCM or TCM and ECU reprogrammed to fix the situation so the converter stays locked up. It may also be possible to "hardwire" the clutch and bypass the controls, but there again, I'm not familiar enough with these to say for sure.
    The other concern I would have is if the trans is strong enough to handle the greater loads present in a marine application? A MUCH different environment from an automobile. The GM transmissions that I have dealt with were heavily modified because of that issue.

    Just some thoughts....

    Thanks,
    Dave
     
  8. Duco84
    Joined: Feb 2014
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    Location: Montenegro

    Duco84 Junior Member

    Thanks. Any idea about solving problem with shifting from D to R?
     
  9. DSR
    Joined: Mar 2017
    Posts: 40
    Likes: 1, Points: 8, Legacy Rep: 10
    Location: Michigan

    DSR Junior Member

    What is the reasoning in looking for something other than a marine transmission for the boat?
     

  10. Duco84
    Joined: Feb 2014
    Posts: 54
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    Location: Montenegro

    Duco84 Junior Member

    There is a few reasons. I hope that I will use 2nd and 3rd gear. Car engines are not so reliable to work long time on rpm hihger than 3000. Definitely this is case with boats. Also consumption. And on end, I alreda have subject transmission.
     
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