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Thread: Marina 4 speed gearbox gearchange extension.

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  1. #1 Marina 4 speed gearbox gearchange extension. 
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    Starting this thread again as we had sidetracked to this in a different thread 'another update'.
    Anyway DC and Darth Vader has given us a great idea and a challenge to fabricate the gearbox extension to save on scraping knuckles on the dash.
    DC, could you add you photos to this again please.
    I had a spare selector extension as it looks like two will be required to make the extended version.
    The housing between the propshaft flange and the gear selector will need to be cut and if two extensions were used then the second could be sacrificed to ensure the housing wall thickness is still there on both parts.
    I have separated the selector housing and cleaned it all up.

    IMG_4018.JPG
    IMG_4019.JPG

    Unfortunately had to sacrifice the rest of the casing to maintain the wall thickness in the selector housing.

    IMG_4020.JPG

    After a bit of origami to get the dimensions.

    IMG_4026.JPG

    Then transferred this to scraps of aluminium that I had hanging around.

    IMG_4028.JPG
    IMG_4029.JPG
    IMG_4030.JPG
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  2. #2 Re: Marina 4 speed gearbox gearchange extension. 
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    A quick trial fit before I continue then decide whether to hack up my gearbox that is already on the engine ready to fit.
    Also took some measurements to make sure it clears the prop shaft and think I will have about 10mm. May need to raise it up and move more centrally to clear the prop and move centrally in the narrow part of the tunnel and use a universal joint to connect the selector rod as hairydave suggested.

    IMG_4031.JPG
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  3. #3 Re: Marina 4 speed gearbox gearchange extension. 
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    A quick trial fit before I continue then decide whether to hack up my gearbox that is already on the engine ready to fit.
    Also took some measurements to make sure it clears the prop shaft and think I will have about 10mm. May need to raise it up and move more centrally to clear the prop and move centrally in the narrow part of the tunnel and use a universal joint to connect the selector rod as hairydave suggested.

    IMG_4031.JPG
    Last edited by meverett; 01-09-2017 at 09:46 PM.
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  4. #4 Re: Marina 4 speed gearbox gearchange extension. 
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    Forgot to add this will move the gear lever back by 7".
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  5. #5 Re: Marina 4 speed gearbox gearchange extension. 
    Club Member dcunn's Avatar
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    As requested, herewith pics - email me at home if you need higher res ones

    Looking good so far Martin

    Rgds DC
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  6. #6 Re: Marina 4 speed gearbox gearchange extension. 
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    Thanks Dave,
    I am now at the stage where I need to remove the selector housing from my existing gearbox already bolted to the engine, do I or don't I? If I b&lls it up I will have to source another extension and partially strip the gearbox down (again) to replace.
    DC, looking at the pics of KEX the tunnel looks parallel where mine narrows to 100mm'ish where the gearchange will be. The gearchange is off centre on the original and to make it central to the tunnel will mean using a universal joint connecting the gearchange shaft.

    IMG_4038.JPG
    Last edited by meverett; 02-09-2017 at 03:14 PM.
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  7. #7 Re: Marina 4 speed gearbox gearchange extension. 
    frequent forum contributor Club Member stevejgreen's Avatar
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    Would it be totally impractical to simply extended the single rail, even by machining a longer one, and devising a clamp or fixing that is less destructive to the standard gearbox?
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  8. #8 Re: Marina 4 speed gearbox gearchange extension. 
    Club Member dcunn's Avatar
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    Martin
    Yes KEX tunnel has a slight taper from the front but mostly parallel sided - note that the lever is off set anyway, and the handbrake lever is not in the normal place either

    I would have thought it possible to get the extra width by cutting the top few inches off the tunnel where you need to and "plating" new straight bits either side, leaving the bottom of each
    side untouched for rigidity and "plating" over the top and down to the floor level ?
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  9. #9 Re: Marina 4 speed gearbox gearchange extension. 
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    I have taken the plunge and cut the old selector off to be able to take some more measurements. Unfortunately to keep the selector shaft in line the modified selector will catch on the prop.

    IMG_4039.JPG

    One question, is the prop shaft reverseable as it would fit no problem if it could be. Ignore the 15mm copper fitting, that won't be used, just there to maintain a straight selector shaft.

    IMG_4040.JPG
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  10. #10 Re: Marina 4 speed gearbox gearchange extension. 
    Club Member dcunn's Avatar
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    Crazy thought...why not weld the back part of the selector shaft onto the top of the old one, then you could put the selector higher up and this would give you the lift required to clear the propshaft - would you still be able to select all gears ?????

    Propshaft probably OK t'other way round, but remember also the rear axle moves up and down so you need a bit of room between your selector thingy and the propshaft, maybe you could also file off a mm or two from the bottom lip ?

    Hope these thoughts help

    Rgds DC
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