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  1. #1
    Join Date
    Feb 2011
    Location
    Northampton
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    41
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    4,021

    Gearbox/pinion angle - also T56 in a Dax

    A couple of questions, really.. we dropped the 'buck' engine and gearbox in over Christmas (see my build thread) and now I'm trying to figure out how to mount the gearbox; Dax (probably back when Gary was doing fab work) added a gearbox mount at the tail end which is shaped like this:



    (Rectangles are a cross-section of the chassis tubes, lines are the plate steel gearbox mount)

    So I've been trying to figure out how high up the tail of the gearbox needs to be - the build manual offers little advice really other than "Put engine and gearbox in, set height with shims, done" - so as I understand it, the aim is to have:
    1. The gearbox output flange and diff input flanges parallel to one another
    2. The gearbox output and diff input should not be in-line with one another
    3. I also thought the diff was meant to point slightly nose-down (which I guess mine does at 89º) and gearbox tail-up, though I've seen some diagrams with them pointing nose-up and gearbox tail-down?


    My diff input flange measures 89º from horizontal according to my digital angle gauge (set to zero with respect to the chassis), and once I've jacked the gearbox tail up to also read 89º I'm going to need an awfully large (90mm tall!) gearbox mount and at that point, it seems like it would have made far more sense to use the 'normal' Dax style gearbox mount plate (which is flat) rather than a dropped one. This makes me think I've got something very wrong..

    FWIW there is zero adjustment in the diff - the diff carrier is solidly bolted to the diff and to the chassis and there is no provision for shims in the Dax carrier or the diff - so the only adjustment I have is to the arse end of the gearbox and/or by shimming the engine mounts to raise the engine.


    Alternatively - has anyone fitted a T56 in a Dax and have pictures of how your (very, very short) driveshaft ended up looking?
    My DeDion build diary..
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  2. #2
    Join Date
    May 2004
    Location
    STOKE ON TRENT, U.K.
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    54
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    10,162
    If you can:-
    Set the engine and box that suits the chassis/tunnel best.
    Make sure they are as "north/south" as possible.
    Then, consider modifying the upper diff mount (make a new one possibly) so that the pinion angle matches the angle of the engine/box.
    I found that following the "Dax advice" of just pointing them at one another would lead to some miss alignment causing a growling/vibration under hard acceleration.
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  3. #3
    Join Date
    Feb 2011
    Location
    Northampton
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    Gotcha - with the gearbox sitting where it 'wants' to it's pretty north/south, but will be facing slightly downward, so the diff nose should point upward by the same amount.. I can achieve that by modifying the upper diff mount to rotate the whole thing backward; assuming I'm understanding you right?

    Way to ruin my day, Dave
    My DeDion build diary..
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  4. #4
    Join Date
    Mar 2009
    Location
    liverpool
    Age
    46
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    377
    Hi Aaron,

    These of any use -

    Drive line calculator

    https://spicerparts.com/calculators/...gle-calculator

    or as you are using a T56 Tremec have an App. Do it all with your phone?

    http://www.tremec.com/menu/tremec-toolbox-app/

  5. #5
    Join Date
    Feb 2011
    Location
    Northampton
    Age
    41
    Posts
    4,021
    Oh, neat app, Phil! I'll compare the results with that to the results of my angle finder .. good sanity check.

    I wonder .. given how much or little the drivetrain length changes, if I can get away with getting the prop made now; the app, at least, wants an angle measurement from the prop too - although I can probably approximate that with a steel rule and both drive flanges
    My DeDion build diary..
    Hon Sec of the Digidash branch of the Unpopular Kit Car Design club

  6. #6
    Join Date
    Feb 2011
    Location
    Northampton
    Age
    41
    Posts
    4,021
    Spent some time with the tremec app and a steel rule.. and I'll be damned if I can find a combination of heights and angles that works, so the diff will have to move.. I'm just not sure it's possible to move enough.

    Shorter gearbox might be required! :/

    Definitely had one of those "shut the door and never want to see it again" evenings in the garage, regretting my choices..
    My DeDion build diary..
    Hon Sec of the Digidash branch of the Unpopular Kit Car Design club

  7. #7
    Join Date
    Nov 2012
    Location
    Lanarks
    Age
    63
    Posts
    223
    The manufacturer got the prop angle bang on right at 90 degress
    Perpendicular to the ground
    Moving it – and upsetting all the geometry ( no way)

    Without seeing your set up..
    The answer is to alter your engine mounts
    Use the dropped gearbox mount to secure the prop end
    and digital angle finder (spirit level) your way to a new set on dropped engine mounts.

    Got to go now
    Edinburgh New Year Party awaits for this auld timer

  8. #8
    Join Date
    Feb 2011
    Location
    Northampton
    Age
    41
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    4,021
    I don't think it's possible to move the engine mounts - down and the sump will be scraping the pavement, up and I'll need a big hole in the bonnet..

    Not to mention I don't have a welder big enough

    Must admit, I'm getting tired of throwing money into the bottomless pit - must be £40k in and no end in sight. Selling it as a part built would at least fund our wedding and then chalk it up t experience.
    My DeDion build diary..
    Hon Sec of the Digidash branch of the Unpopular Kit Car Design club

  9. #9
    Join Date
    Mar 2009
    Location
    liverpool
    Age
    46
    Posts
    377
    Hi Aaron,

    Sorry, didn't mean to ruin the rest of the year for you.

    With the front mounts fixed it still leaves some adjustment between the gearbox mount and the diff mount or is the prop angles so great with only being a short length?

  10. #10
    Join Date
    Jan 2002
    Location
    Reading, Berks, UK.
    Posts
    1,582
    Aaron

    How much out or to put it another way what is the alignment now like.?
    Form the thread I cant actually work out what sort of angle your prop goes thru or the length of prop you may need.

    You know I have the 460 with the HD Tremec, and my g/box flanges and diff are not directly aligned, the prop is approx. 300mm long, I don't get any issues.
    Just wondering if the difference you may be trying to correct isn't actually going to make any difference at all.

    Can you do a sort of drawing with engine/box and then diff with the prop angle between so we can see.

    I know my chassis is different but I used the std Dax flat plate gearbox mount and std Tremec mounting rubber.

    Pics paint a 1000 words so to speak.

    Don't give in, you are almost there old chap.

    Merry New Year

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