why does this happen on your car ?

northernneil
northernneil Posts: 1,549
edited June 2010 in The bottom bracket
when you some times try to put it into gear before you start the engine it wont quite go in, then as soon as you start the engine whilst pushing the lever it glides straight in ?

there is no purpose to this thread except it I cant understand a technical reason why this would happen, its done it on all the car I have owned.

Comments

  • beatsystem
    beatsystem Posts: 118
    because the gears are not "lined up" sometimes when the engine is off, when running you have syncro mesh which enables this to happen,
  • waynej
    waynej Posts: 56
    In a car, gearboxes are syncromesh - the gears are engaged to each other all the time, when you change gear your actually changing which gears are engaged to the drive shafts. The gears not being used for drive freely rotate on the output shaft.

    To engage a gear, 'dogs' on the gears and the shaft engage with each other, stop free rotation and turn the output shafts. Any gears that were engaged are disengaged (2 gear ratios can't drive the same shaft).

    The 'dogs' are clashing slightly. When the engine starts the shafts start spinning and the dogs can engage easier.
  • beatsystem
    beatsystem Posts: 118
    i stand corrected
  • northernneil
    northernneil Posts: 1,549
    beatsystem wrote:
    i stand corrected

    I sit down with greater knowledge
  • rake
    rake Posts: 3,204
    there are also conical friction plates to match the gears to the same speed before engaging so you dont need to double declutch like the old days.
    i loiter with useless knowledge.
  • prawny
    prawny Posts: 5,440
    Why does my car only go into reverse if I'm moving forward slowly?
    Saracen Tenet 3 - 2015 - Dead - Replaced with a Hack Frame
    Voodoo Bizango - 2014 - Dead - Hit by a car
    Vitus Sentier VRS - 2017
  • batch78
    batch78 Posts: 1,320
    Because you drive something shitty and French???
  • tlw1
    tlw1 Posts: 22,187
    batch78 wrote:
    Because you drive something shitty and French???
  • rake
    rake Posts: 3,204
    probably because of no friction plates (synchromesh) on reverse,like the vast majority of cars french or otherwise (its cheaper). the gear teeth are actually being lined up on reverse rather than just the synchro collars on forward gears.
    you can see here. notice the actual straight cut (not helical cut thats why reverse gear wines) reverse gear moving.
    http://auto.howstuffworks.com/transmission.htm
    as your car rolls forward it turns the reverse gear untill they line up,
  • syncro
    syncro Posts: 120
    prawny wrote:
    Why does my car only go into reverse if I'm moving forward slowly?

    Letting the clutch out slightly just to the bite point also has the same effect as moving forward slightly.
  • pst88
    pst88 Posts: 621
    rake wrote:
    probably because of no friction plates (synchromesh) on reverse,like the vast majority of cars french or otherwise (its cheaper). the gear teeth are actually being lined up on reverse rather than just the synchro collars on forward gears.
    you can see here. notice the actual straight cut (not helical cut thats why reverse gear wines) reverse gear moving.
    http://auto.howstuffworks.com/transmission.htm
    as your car rolls forward it turns the reverse gear untill they line up,
    Oh, so that's why if you rev a little bit and stick it in reverse there is a crunch noise but if you rev a bit and stick it in first gear there is no crunch. Also always wondered about the whine in reverse. Very informative post.
    Bianchi Via Nirone Veloce/Centaur 2010
  • pst88
    pst88 Posts: 621
    I have a question. Say I'm accelerating in 2nd, reach 40mph, I want to change straight into 4th, put the clutch down, move the stick to 4th, I get a horrible grinding noise trying to get into 4th (whilst the clutch is still down). Obviously the solution is to not drive like this and change gear earlier, just wondering why the car does like this. Is it because the jump is too big for the synchros to handle? And yes, I drive something shitty and french.
    Bianchi Via Nirone Veloce/Centaur 2010
  • keef66
    keef66 Posts: 13,123
    I believe you have just answered your own question
  • prawny
    prawny Posts: 5,440
    batch78 wrote:
    Because you drive something shitty and French???

    My car is not french, how very dare you.

    I'm not disputing the fact that it's shitty.

    Why is it that sometimes on my car the handbrake button ping out of the handle and hits the stereo.

    Also why is it that on my car the air con doesn't work.

    Why did I not google c-max problems before I bought my car. :cry:
    Saracen Tenet 3 - 2015 - Dead - Replaced with a Hack Frame
    Voodoo Bizango - 2014 - Dead - Hit by a car
    Vitus Sentier VRS - 2017
  • GiantMike
    GiantMike Posts: 3,139
    prawny wrote:
    Why is it that sometimes on my car the handbrake button ping out of the handle and hits the stereo.
    Because your stereo is where the 'handbrake button catcher' should be.
    prawny wrote:
    Also why is it that on my car the air con doesn't work.
    Because the air-con gasses need re-charging? Halfords do a DIY refill kit, or a monkey from Ford can f*ck it up for you.
    prawny wrote:
    Why did I not google c-max problems before I bought my car. :cry:
    Because you spend you internet time buying bike bits?
  • Roscobob
    Roscobob Posts: 344
    I was laughing there until I realised that my car is shitty and french :cry:
  • rake
    rake Posts: 3,204
    pst88 wrote:
    I have a question. Say I'm accelerating in 2nd, reach 40mph, I want to change straight into 4th, put the clutch down, move the stick to 4th, I get a horrible grinding noise trying to get into 4th (whilst the clutch is still down). Obviously the solution is to not drive like this and change gear earlier, just wondering why the car does like this. Is it because the jump is too big for the synchros to handle? And yes, I drive something shitty and french.
    yes. the difference in gear speeds is greater from missing one out, if you paused a little with light pressure on the lever to give the synchro more time to match the speeds it shouldnt grind. its easier on the box as well not to slam gears to quickly.
  • rake
    rake Posts: 3,204
    just dont buy a hyundai trajet people carrier, a design fault means 2nd gear synchro will give up at moderate mileage meaning a large grind and bang when going to 2nd. when this happens the other gears will get clunky as well. being a specialist unit the gearbox, and an engine out job a very costly replacement or recondition is the only option usually rendering the car economically unviable.
  • outofbreath2
    outofbreath2 Posts: 216
    prawny wrote:
    [
    Why is it that sometimes on my car the handbrake button ping out of the handle and hits the stereo.

    Also why is it that on my car the air con doesn't work.

    It's not that bl00dy Wiggle causing problems again is it...

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