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Transmission or differential mounts....

Discussion in '365 GT4 2+2/400/412' started by Arvid, Jan 4, 2013.

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  1. Arvid

    Arvid Formula Junior

    May 28, 2012
    668
    Norway
    Full Name:
    Arvid Andersson
    #1 Arvid, Jan 4, 2013
    Puzzling over a problem here.....

    I can feel a slight judder in the car when pressing the clutch and selecting 1'st gear,just before taking off. It feels like a sideways movement from the gearbox. It is only happening when I select gear,not when I'm taking off

    I can't find any rubber mounts for gearbox in the partslists but instead I've been told that the mounts for the rear differential are a common problem on these cars.

    Can the rear mounts cause the problem I'm having ? I am not sure. I thought that defect mounts in the rear would be noticable when accellerating. My problem only occures when I press the clutch and select gear and then the propeller shaft is not turning. There should be no force applied to the differential before I let out the clutch,ergo no judder.....?

    I have not checked under the car because I'm fairly certain the problem is either transmission mounts or maybe the diff.

    Any thoughts ?
     
  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,799
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #2 Steve Magnusson, Jan 4, 2013
    One simple test that you can try is, when at rest with the clutch pedal depressed, instead of going from N to 1st, go from N to 3rd, then (quickly, but smoothly) 3rd to 1st (while always holding the clutch pedal depressed). If the 3rd to 1st motion is better than the N to 1st motion = probably indicates that the clutch mechanism is not fully disengaging (mis-adjusted, pilot bearing dragging, etc.). Just a thought (that won't get you greasy ;))...
     
  3. Arvid

    Arvid Formula Junior

    May 28, 2012
    668
    Norway
    Full Name:
    Arvid Andersson
    #3 Arvid, Jan 4, 2013
    Good point Steve :) I have not thought of that since the feel of the clutchpedal seems normal. It engages normaly,not to far in or out.

    Could it still be something misalligned or -adjusted ?
     
  4. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,799
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #4 Steve Magnusson, Jan 4, 2013
    Last edited: Jan 4, 2013
    Having the clutch pedal force and engagement/disengagement points seem reasonable is a good sign for the clutch itself. I don't have access to the 400GT WSM, but your OM indicates that the freeplay at the top of the pedal movement should be 0.6"~0.8" (to keep pressure off the throwout bearing when the pedal is in the full up position, but not be so large that it limits the disengagement when the pedal is in the down position). Usually as the clutch disk wears, the problem (if not readjusted) becomes clutch slippage when the clutch pedal is up (and the throw-out bearing getting worn out prematurely) -- so not really your symptom. However, a "dragging" pilot bearing or something being warped in the flywheel/clutch disk/pressure plate sandwich could give your symptom.

    But try the test first -- if it makes no difference, then the problem probably lies elsewhere. If it does make a difference, check the adjustment -- if not OK, readjust (and hope ;)). If the adjustment seems OK (but the problem is still there), then you'll (unfortunately) probably have to go in deeper to the clutch or the gearbox itself.
     
  5. Arvid

    Arvid Formula Junior

    May 28, 2012
    668
    Norway
    Full Name:
    Arvid Andersson
    #5 Arvid, Jan 4, 2013
    The clutch is fairly new,low on km and has a good strong feel to it,so I am hoping ;-) The car has two owners prior to me,the last one aged 83... Old men and stiff knees is a rather common combo in Norway,probably the case in Germany where the car originates as well.... So how good the clutch really is remains to be seen.

    I will do a test of what you suggested,maybe that can reveal something. Could be as simple as an adjustment.

    Thanks for good advice Steve :)
     
  6. Ak Jim

    Ak Jim F1 Veteran
    Owner Rossa Subscribed

    Dec 23, 2007
    9,621
    North Pole AK
    #6 Ak Jim, Jan 4, 2013
    Back to the original question (even though probably not the problem) there are a total of four mounts, two on the engine and two on the differential. While I'm not sure I think they are all the same. The torque tube holds the engine/transmission assembly rigidly to the differential.
     

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