308 missing 4th & 5th on track at high speed | FerrariChat
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308 missing 4th & 5th on track at high speed

Discussion in 'Technical Q&A' started by atlantaman, Oct 31, 2004.

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  1. atlantaman

    atlantaman Formula 3

    Mar 31, 2002
    1,726
    Roswell, Georgia
    Full Name:
    Charles
    #1 atlantaman, Oct 31, 2004
    Just thought I would throw this one out----

    My 308 had been running flawlessly until I got ont he track this weekend.
    Now when I am under heavy throttle or when in right turn, I try to shift into 4th or 5th and there is nothing. Under normal running everything is fine

    I thought my shifter linkage was just off--so i readjusted it--now thinking maybe the rubber in the motormounts????

    any ideas?
     
  2. ferrarifixer

    ferrarifixer F1 Veteran
    BANNED

    Jul 22, 2003
    8,520
    Melbourne
    Full Name:
    Phil Hughes
    #2 ferrarifixer, Oct 31, 2004
    If the adjustments are perfect, then it must be the mounts or the shift bushes.

    To check for radial gear link adjustment perfection, unscrew the gate, select 3rd and rock the lever left and right while in 3rd with the gate lifted out the way.

    The movement each way should be the same if the shift is set central.
     
  3. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    405
    Ferndale, WA
    #3 Matt Morgan, "Kermit", Nov 1, 2004
    While you are at it checking mounts, it would be a good idea to check the Reaction Rod, as it is a major factor in alignment of the engine under power. It's worth a look, although IMO, it sounds like a motor mount weakness causeing a shift rod binding due to a movement in the entire unit. Power causing a problem would show up in either one gear or the other, not both, due to engine rocking fore and aft, and the tip off of right hand turns would indicate a binding of the shift rod.
    HTH
    Kermit
     
  4. pad

    pad Formula 3

    Sep 30, 2004
    1,426
    Tequesta, FL
    Full Name:
    Paul Delatush
    #4 pad, Nov 1, 2004
    Nothing like a good day at the track to shake up motor mounts. Had the same issue on both my 308 and Etype Jag. It's now part of the spring ritual to check/change mounts on both cars.
     
  5. atlantaman

    atlantaman Formula 3

    Mar 31, 2002
    1,726
    Roswell, Georgia
    Full Name:
    Charles
    #5 atlantaman, Nov 2, 2004
    Kermit--i think i need to clarify a bit

    Savannah is a 80% 4th gear track

    When taking the long right sweeper coming into the straight i would shift to 5th and the gate would be "empty" , i would shift back to 4th and also empty... I would have to drop it into 3rd and then back into 4th and 5th GENTLY and all would work fine.

    The only time this happens is under hard acceleration .. And I have a very solid stainless reaction bar

    i will play with the linkage some this weekend---just hoping that nothing in the forks or in the tranny could be outta whack
     
  6. Verell

    Verell F1 Veteran
    Consultant Owner

    May 5, 2001
    7,022
    Groton, MA
    Full Name:
    Verell Boaen
    #6 Verell, Nov 2, 2004
    Loosing a pair of gears under hard acceleration around a sweeping curve is likely to be due to your engine tilting towards the outside of the curve, possibly due to a motor mount on the end of the motor towards the inside of the curve that's lost a thru bolt, or is broken.

    Get enough tilt (10-15 degrees is all it would take!) and the transmission will have rotated enough so that the arm on the end of the shift shaft slips outside the end of the yoke on the end of the 4th-5th gear L-arm that slides the 4th-5th yoke's shaft. If the shift shaft is slightly out of adjustment, it could take even less tilt.

    If you don't find anything with the motor mounts, then bite the bullett & pull the tranny sump cover. You'll need someone in the cockpit to work the shift rod. It's very easy to see how the trans shift shaft works & access everything with the sump cover off. I'd check to see if the L-arm on the end of the shift shaft is slightly loose (or more likely just slightly miss-aligned). Also check the 4th-5th gear yoke to make sure it's not slightly loose on it's shaft. That entire transmission is very rugged, highly unlikely that anything's broken, but things are known to occasionally loosten up & slip slightly under pressur.

    CAUTION:
    If you pull the sump cover, watch out for the 3 springs & balls vertically in the edge of the trans. housing. They're held in place by the clutch end of the cover. Usually they'll stick in their holes, but 1 or 2 usually drop out. (Search the archives of a few months ago, there are some good photos of these springs, balls & the tranny internals).
     

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