365GTB/4 (Daytona) Ring Gear Backlash? | FerrariChat
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365GTB/4 (Daytona) Ring Gear Backlash?

Discussion in 'Vintage (thru 365 GTC4)' started by Motob, Jul 28, 2025 at 4:20 PM.

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  1. Motob

    Motob Formula 3
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    #1 Motob, Jul 28, 2025 at 4:20 PM
    I am installing a used ring and pinion from one transaxle into the housing of a different transaxle.
    I have the pinion height set and have a pretty good gear pattern and need to adjust the backlash.

    The factory shop manual lists the backlash clearance as " not to exceed 0.03mm-0.04mm (0.0012"-0.0016"), and at the point where the teeth are closer, there should be no forced effort noted" So Ferrari essentially wants
    0.000 to 0.0016" backlash.

    When compared to other differential backlash specifications this seems awful tight to me. If there is any expansion of the gears, the clearance is going to close up and there will be excessive pressure on the teeth, causing noise, friction/heat and wear. Maybe the housing expands faster than the gears, causing them to move away from each other with heat?

    Does anyone have an alternative backlash specification that they trust, and knows that works on a Daytona transaxle?

    Thanks!
     
  2. TTR

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    #2 TTR, Jul 28, 2025 at 5:11 PM
    Last edited: Jul 28, 2025 at 5:17 PM
    Are you sure about this 0.04mm as the range (from 0.03mm to 0.04mm) seems awfully narrow or should I say almost non-existent at 0.01mm (=0.0004") ?

    It's been awhile since did one & don't have my notes handy, but will try to check them later this week.
     
  3. TTR

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    #3 TTR, Jul 28, 2025 at 5:57 PM
    What backlash clearance other, same era transaxles (i.e. 275GTB/4, 330/365GTC, etc) call for ?
     
  4. Motob

    Motob Formula 3
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    #4 Motob, Jul 28, 2025 at 10:58 PM
    The factory Daytona manual lists the .03-.04mm spec in two places, so I have to believe that it is what they wanted. It is also listed as the maximum "not to exceed" which seems awfully tight to me.
    I have not seen what the other manuals call for. I will see if it is listed in the 275 2 cam manual. I don't have a 330GTC manual.
     
  5. fasthound

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    #5 fasthound, Jul 29, 2025 at 7:42 AM
  6. TTR

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    #6 TTR, Jul 29, 2025 at 12:27 PM
    Last edited: Jul 29, 2025 at 12:33 PM
    Brian, I agree the backlash clearance numbers seem (too ?) tight and as I mentioned (right or wrong) the range also seems a bit narrow, but it wouldn’t be first time I found factory manuals/literature related to 365GTB/4s having (unintended ?) data/information inaccuracies.

    Also, while I’ve never received any formal education in English (or in mechanical/technical engineering or related skills training) I’ve found Mr. A. Wallace’s translation of the factory WSM for 365GTB/4 somewhat lacking on technical accuracy & clarity.

    Kevin, the page you posted appear to refer to clearance/tolerance spec’s on the transmission side of the (330GTC ?) transaxle.
    If you can find & post backlash spec’s for the differential ring & pinion, it might prove helpful for comparison.
     
  7. fasthound

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    #7 fasthound, Jul 29, 2025 at 1:39 PM
    TTR…yep, wrong specs…sorry. And yes, for 330GTC as noted above the photo.

    Here are the pinion/ring gear specs from the 330GTC workshop manual for direct comparison:

    “In the correct operating position, the backlash clearance between the pinion and ring gear must not exceed 0.02 to 0.03mm, and at the point where the teeth are closest, there should be no forced effort noted.”

    So, even tighter than the Daytona specs.
     
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  8. TTR

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    #8 TTR, Jul 29, 2025 at 2:20 PM
    Brian, do you by chance have an access to someone with OEM WSM and technical level fluency in Italian language ?
    I have a feeling something might’ve gotten lost or misinterpreted in translation.
     

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