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Thunk When I Take Off From a Stop

Discussion in 'Technical Q&A' started by hanknum, Mar 7, 2006.

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  1. hanknum

    hanknum Formula 3

    Nov 1, 2003
    2,050
    Santa Barbara
    Full Name:
    Henry
    #1 hanknum, Mar 7, 2006
    Just recently (after I did my belts, tensioners, valve adjustment, etc) I noticed that a light "thunk" when I take off from a light, sometimes. This seems to happen about half the time. The car is a '78 308 GTS. It may very well be coincidence for it starting after the service. My first thought was I didn't tighten the reaction rod, nope, it was tight. Anyone have any thoughts?

    Thanks

    Henry
     
  2. Verell

    Verell F1 Veteran
    Consultant Owner

    May 5, 2001
    7,022
    Groton, MA
    Full Name:
    Verell Boaen
    #2 Verell, Mar 7, 2006
    If not reaction rod, then ck the motor mounts.
     
  3. 88MONDIAL

    88MONDIAL Formula 3

    Apr 13, 2005
    1,052
    Racine, Wisconsin
    Full Name:
    Jim Smith
    #3 88MONDIAL, Mar 7, 2006
    I'm not mechanically inclined, but over 10 years ago my Porsche 944 did that. It was the half-shafts that needed replacement. Just would be odd for that to be the case after your service, might want to look into it though. Good luck.
     
  4. DGS

    DGS Seven Time F1 World Champ
    Rossa Subscribed

    May 27, 2003
    70,467
    MidTN
    Full Name:
    DGS
    #4 DGS, Mar 7, 2006
    From the engine or the calipers?
     
  5. hanknum

    hanknum Formula 3

    Nov 1, 2003
    2,050
    Santa Barbara
    Full Name:
    Henry
    #5 hanknum, Mar 7, 2006
    Good questiion. I was thinking from the engine, but I'll put it up in the air this weekend and spin the wheels to make sure it isn't a sticking caliper.
     
  6. Perfusion

    Perfusion F1 Rookie

    Oct 16, 2004
    4,151
    Marietta, GA
    Full Name:
    Aaron
    #6 Perfusion, Mar 7, 2006
    I get it as well in my 308GT4... The first thing that came to my mind was, "motor mounts." I'll have to have a look - if I even can - next time the car is up in the air.
     
  7. Ricambi America

    Ricambi America F1 World Champ
    Sponsor Owner

    Dec 7, 2003
    16,417
    Winston Salem, NC
    #7 Ricambi America, Mar 7, 2006
    I bet a hard shift from 2 to 3 will cause the same sound. Try that, and report back.
     
  8. Perfusion

    Perfusion F1 Rookie

    Oct 16, 2004
    4,151
    Marietta, GA
    Full Name:
    Aaron
    #8 Perfusion, Mar 7, 2006
    Will do this weekend.
     

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