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365 GT 2+2 Gearbox rebuild

Discussion in 'Vintage (thru 365 GTC4)' started by Peter Lipman, Dec 24, 2020.

  1. Peter Lipman

    Peter Lipman Rookie

    Nov 24, 2020
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    Full Name:
    Peter Lipman
    I am a new 365 GT 2+2 owner and am experiencing what i understand to be common which is the synchros being worn in the gearbox making shifting a grind, so to speak. Does anyone have experience rebuilding the gearbox for this issue? Which components on the main and lay shafts would be the candidates to replace? Is it difficult to disassemble and replace components? Any special tools needed? Better to have a pro do it? Any other advice? thanks
     
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  3. shoreorthopod

    shoreorthopod Karting

    Oct 14, 2012
    94
    Have a pro do it.... these boxes can be very tricky...tom yang did mine a few years ago and it shifts like a dream
     
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  4. V12addict

    V12addict Karting

    Jan 2, 2004
    108
    Agree, take the whole transmission out and do a full re build by a pro shop. You will be happier in the long run and the car deserves it.The 365 gt 2+2 is a fabulous car and you won't regret it.
     
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  5. Tegethoff

    Tegethoff Karting
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    Jul 19, 2014
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    Los Feliz
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    Adam
    #4 Tegethoff, Dec 25, 2020
    Last edited: Dec 25, 2020
    Generally, 3 of 521767 and 1 each of 521768, 521769 are required, but if there is severe wear , 3 of 522047 may be a good idea. All new bearings would be a smart move too.

    As previously mentioned, unless you have experience, specialty tools and technical information, get it done professionally. It's not rocket surgery, but it's complex enough that I wouldn't want to be R&Ring the tranny multiple times to get it right.

    Here's a pic with the sliders and rings highlighted, it doesn't include 5th which is on the output shaft, but it's basically the same parts and assembly.
     

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  6. Bowzer

    Bowzer Karting

    Aug 3, 2016
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    MALTA
    Full Name:
    Marcus
    Send it to an experienced professional and you will love it for another 50 years if cared for. The car will be grateful for it and you can enjoy a true marvel of a car.
     
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  8. Peter Lipman

    Peter Lipman Rookie

    Nov 24, 2020
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    Peter Lipman
    This is very helpful. i am a little confused by one thing though. In my experience with worn synchros, it is the teeth that are worn down and rounded. I am having trouble understanding exactly the role of these synchro rings and why replacing them makes the gears sync better again.
     
  9. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    6,533
    southwest germany
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    romano schwabel
    the synchros have a cone and this cone is connecting to the gears and bring them to the same rpm as the shaft. and after then the sliding sleeve will connect to the teeth.
    so the new synchros are a little thicker in the inside diameter becaus ethey are not worn out as used ones
     
  10. 330gt

    330gt Formula 3

    Nov 12, 2004
    1,748
    Seattle, WA
    Full Name:
    Kerry Chesbro
    Note, there are two different models of the 365 2+2 transmission, so be sure and use the correct parts manual that matches the car.
     
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  11. Tegethoff

    Tegethoff Karting
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    Jul 19, 2014
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    Adam
    You are most likely thinking of a different style of synchronizer assembly. Like this image from a Tremec T5:
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    In this style assembly the blocker ring has "sacrificial" brass/bronze teeth that guide the slider onto the dog teeth of the gears. The blocker ring also acts as the clutch to match the differing speeds of shaft and gear.

    In your transmission and most older Ferrari transmissions, the sacrificial teeth are not present on the blocker ring, and the slider directly engages the dog teeth on the gear. I believe the slider is slightly softer than the gear and takes most of the wear.

    If you do have worn dog teeth, the entire gear needs to be replaced. This is why later designs from Getrag use a blocker ring with teeth as it helps prevent wear to the dog teeth. If the transmission has been operated for a long time with worn blocker rings, you may infact need new gears, especially 2nd and 3rd as they tend to take the brunt of full throttle shifts.
     
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