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F355 Final Drive

Discussion in 'Technical Q&A' started by charleswan, Dec 22, 2003.

  1. charleswan

    charleswan Rookie

    Dec 22, 2003
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    Hong Kong
    Full Name:
    Charles Wan
    Does anyone know whether there's any difference with the final drive on the 355 ?

    I know the US version is with 4.35 but is the Euro version different ?

    Can we use other model's final drive ? Like 348's for example ?

    I need a shorter final drive to increase acceleration.

    thanks
     
  2. Ferrari_tech

    Ferrari_tech Formula 3

    Jul 28, 2003
    1,527
    UK
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    Malcolm W
    The european final drive ratio is 3.56 :1, which would appear to be the same as the US version (see table below)

    The 348 final drive ratio is also 3.56 :1, but anyhow would not fit into a F355.

    What about alternative wheels / tyres ?


    MW
     
  3. charleswan

    charleswan Rookie

    Dec 22, 2003
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    Charles Wan
    Thanks for your reply,

    So the 4.35 final drive is for the Challenge only ?
    Can you verify that ?

    Can we just get this gear set for the street version 355 ?

    much thanks and appreciation from your reply !

    Charles
     
  4. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
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    Steve Magnusson
    What is your reference for the 4.35:1 final drive ratio? Seems too low for a high-speed (150+ MPH) GT. I know in 308-land this often gets very confused because "final drive" can mean:

    1. diff gear ratio only
    2. gearbox ratio only (i.e., 5th gear ratio x diff ratio)
    3. true overall engine-to-wheels ratio (i.e., transfer gear ratio x 5th gear ratio x diff ratio)

    Don't know the exact components involved a 355 drivetrain, but I just wanted to warn you that spec translations can get messed-up this way.
     
  5. charleswan

    charleswan Rookie

    Dec 22, 2003
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    Charles Wan
    Dear MW,

    I've just checked with my manual and it says this .. mine is a 2.7 Motronic UK Spec. car.

    1st = 15:46 = 0.326 = 3.066
    2nd = 19:41 = 0.463 = 2.157
    3rd = 23:37 = 0.621 = 1.608
    4th = 26:33 = 0.787 = 1.269
    5th = 29:30 = 0.966 = 1.034
    6th = 37:31 = 1.193 = 0.837
    RM = 15:42 = 0.357 = 2.8

    Final Drive = 16/57 = 3.5625
     
  6. charleswan

    charleswan Rookie

    Dec 22, 2003
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    Charles Wan
    And the Challenge is with 4.35
     
  7. Aircon

    Aircon Seven Time F1 World Champ

    Jun 23, 2003
    77,526
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    Peter
    I have never seen anything that suggests anything different in the gearbox/diff of a 355 challenge compared to a standard 355.
     
  8. wax

    wax Four Time F1 World Champ
    Advising Moderator

    Jul 20, 2003
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    Dirty Harry
    Google Results for: "ferrari 355" final drive displays Final Drive Ratio, 4.35:1 all over the place. Whether that's gospel or not, I don't know. But that's what some are preaching.
    ___

    Search trick: Enclose main search criteria within quotes, other search criteria outside quotes. Hence, the above "ferrari 355" final drive

    If you wish to exclude a certain term/result, but retain others, then do it like this: "ferrari 355"-final drive
    In this case, forget about seeing any final drive ratios, but count on seeing drive in addition to "Ferrari 355".

    But, if you don't want to see final or drive, then do this: "ferrari 355"-final-drive
     
  9. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    6,337
    Whooaahh.

    The F355 transmission has several more gears these are used to drop axes and turn corners.

    There is a spur gear that moves power from the cranckshaft concentric axis to the shaft axes (e.g. lower by 3") of the F355 suspension. 25:29 = 1.160

    There is a 90 degree bevel gear converting longitudinal rotation into tranverse rotation. 19:20 = 1.052 It is important that this gear be as close to 1:1 as possible for power efficiency reasons. However, it is also important that this gear not be 1:1 for noise reasons as it operates at engine speed rather than road speed (as on most driveline arrangements.)

    Differential feeder 16:57 = 3.562. This is a straight transfer gear from the output shaft to the differential carriers

    4.35 = 3.562 * 1.160 * 1.052
     
  10. charleswan

    charleswan Rookie

    Dec 22, 2003
    40
    Hong Kong
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    Charles Wan
    So Mitch,

    Do you suggest that by physically lowering the car by 3", the final drive ratio will translate to 4.35 ?

    Can you please say english ?

    thanks

    Charles
     
  11. Ferrari_tech

    Ferrari_tech Formula 3

    Jul 28, 2003
    1,527
    UK
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    Malcolm W
    Charleswan,

    As far as I can recall the 355 Challange cars had a standard 355 diff ratio of 3.56 :1, so I'd be interested to know where you got 4.35 :1 from.

    I had a look throught the Challange rules and regulations and found the following references to "gearbox" - it reads :-

    "The gearbox must remain as originally supplied with the car. (The Swiss version is considered equal to the European version) It is permitted to install a reinforced 3rd & 4th speed selector fork under part no. 167315 in place of the genuine part 157162"

    I may be wrong - comments welcomed

    MW
     
  12. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,166
    Texas
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    Steve Magnusson
    I've got to say that using/comparing these types of numbers all made a lot more sense with a 1:1 top gear transmission bolted directly to the engine crankshaft driving a simple differential ;). Mitch is giving:

    transfer gear ratio x bevel gear ratio x differential gear ratio = 4.35:1

    and

    MW just the differential gear set ratio = 3.56:1

    and IMO neither is the true "final drive" ratio which would be Mitch's number x the 0.837 6th gear ratio = 3.64:1

    Pick any of the three you like ;)
     
  13. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    6,337
    The transmission sits tranversally under the rear axles.

    The crankshaft axis is 3" higher than the axes of the gear clusters. So one gear is used to drop from the centerline of the crankshaft (and clutch) to the centerline of the gear clusters. A chain could have been used here instead of a gear.

    The engine and clutch are mounted longitudinally while the gear clusters and output shaft are mounted transversly. A pinion gear is used to make this 90 degree axis change.

    The heavy parts of the transmission is some 5" lower than in a Viper or Vette. The car was not lowered, but the gear clusters are lower than the centerline of the engine.
     

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