shift shock - is there no way to avoid it when driving hard/fast?

Discussion in 'The Garage' started by BlahBlahYouToo, Mar 7, 2008.

  1. BlahBlahYouToo

    Joined:
    Jul 10, 2007
    Messages:
    12,062
    Likes Received:
    0
    happens to me, my friends, watching professional driver videos on youtube, etc.
    is that just a necessary evil of trying to shift as fast as possible during high rpm?
    is it bad for the clutch/engine/drivetrain?
     
  2. DivideBYZero

    DivideBYZero Lifer

    Joined:
    May 18, 2001
    Messages:
    24,119
    Likes Received:
    0
    Any hard shift is going to have a greater impact on the drivetrain than normal, but I'm going to assume that you don't drive on a track/do it every day so don't worry about it.
     
  3. Zenmervolt

    Zenmervolt Supermoderator<br>The Garage<br>Elite member
    Super Moderator

    Joined:
    Oct 22, 2000
    Messages:
    24,522
    Likes Received:
    0
    It's actually easier on the clutch's friction material than a smooth shift is because there's not nearly as much slip during take-up. However, it stresses the springs in the clutch center more and is harder on the entire drivetrain. In most cases though you have to be almost abusively hard with the shift to cause issues. (Note that some specific cars are more or less durable than others, the original WRX supposedly is not as durable, the Honda S2000 has reports of issues with the CV joints in the rear halfshafts, and the Porsche 944 non-turbo has a weak differential; these are just examples to illustrate the importance of knowing your particular vehicle's strong and weak points and even these cars require very abrupt shifting to cause damage.)

    ZV
     
  4. Arkaign

    Arkaign Lifer

    Joined:
    Oct 27, 2006
    Messages:
    19,305
    Likes Received:
    0
    I used to constantly snap axles on my 5g prelude :( I usually got about 20k miles out of a set. They just weren't designed for boost + high-rpm launches.
     
  5. helpme

    helpme Diamond Member

    Joined:
    Feb 6, 2000
    Messages:
    3,090
    Likes Received:
    0
    Wheel hop kills Axles on the SRT-4 as well :(
     
  6. mooseracing

    mooseracing Golden Member

    Joined:
    Mar 9, 2006
    Messages:
    1,712
    Likes Received:
    0
    wheel hop kills any axles or driveshafts.
     
  7. Vic

    Vic Elite Member

    Joined:
    Jun 12, 2001
    Messages:
    39,611
    Likes Received:
    10
    On hard driving, I mesh the clutch out like 0.001th of a second before going back WOT. The idea is to damp the revs down from the prior gear just enough to match with the next gear yet while upshifting as quickly as possible. It's difficult to explain and takes considerable practice, but done right there is little to no shift shock, just Go, shift, Go, shift, Go...
    This is IMO faster than the hard-shifting barking gears technique, and 110% nicer to the equipment.
     
  8. yelo333

    yelo333 Senior member

    Joined:
    Dec 13, 2003
    Messages:
    991
    Likes Received:
    0
    Can you please elaborate? It seems like what you are describing is the "normal" way to do a hard shift. How is what you do different?

    Here is what I think you are saying:

    1) WOT
    2) foot off gas
    3) clutch in
    4) move shift lever
    5) clutch out
    6) WOT (0.001 seconds later)

    The result of this in my car is a thud noise of what I assume is the engine rocking a little, a slight forward jolt and an instant pitch change.

    Is this what you are saying?
     
  9. Vic

    Vic Elite Member

    Joined:
    Jun 12, 2001
    Messages:
    39,611
    Likes Received:
    10
    Reverse steps 2 and 3. Clutch should always go in slightly before you come off the gas.

    If you're getting shift shock like the OP described, the only way that could happen is if go back WOT with the clutch out and the revs still up above what is necessary (matched) for the next gear in the upshift.

    A corollary is the way race bikes use an automatic switch to briefly kill the ignition between shifts so the rider doesn't have to come off the throttle.
     
  10. Zenmervolt

    Zenmervolt Supermoderator<br>The Garage<br>Elite member
    Super Moderator

    Joined:
    Oct 22, 2000
    Messages:
    24,522
    Likes Received:
    0
    Yup, Vic's got it right. There's usually still a little "surge" as you are landing back in the meaty part of the powerband if the gear ratios are right, but there shouldn't be a "slamming" sensation.

    ZV
     
  11. DivideBYZero

    DivideBYZero Lifer

    Joined:
    May 18, 2001
    Messages:
    24,119
    Likes Received:
    0
    The only time I would expect a real jolt would be if you were keeping the throttle open during the shift. This normally only happens in rental cars.... :p
     
  12. Zenmervolt

    Zenmervolt Supermoderator<br>The Garage<br>Elite member
    Super Moderator

    Joined:
    Oct 22, 2000
    Messages:
    24,522
    Likes Received:
    0
    It was fun to do in the Mustang when I had it... ;) But the Tremec transmission in the Mustang GT is incredibly overbuilt for that application so it's not apt to break.

    ZV
     
  13. DivideBYZero

    DivideBYZero Lifer

    Joined:
    May 18, 2001
    Messages:
    24,119
    Likes Received:
    0
    Yeah, I'm not a great fan of power shifting, I don't think you get much more out of it vs. applying WOT as soon as you've engaged the clutch. For me, as I have been driving manuals almost exclusively for almost 18 years, it's actually hard to keep the gas pedal down during a shift. It's just second nature to lift a little at least.

    Oh, BTW, going for a track session in an Exige soon around Thruxton race circuit with 1 to 1 tuition. Should be a hoot!