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Software Update - 7 spd gearbox.

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by exjag, Jan 5, 2013.

  1. exjag

    exjag Senior Member

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    I've been reading with interest the sticky about, amongst other things, the software update for the seven speed auto gearbox and wonder what exactly was the defect it fixed?

    Can anyone please describe the symptoms of the fault? (HAWK20 ??)

    Many thanks.
     
  2. television

    television Always remembered RIP

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    The main complaint was hard changes fro 1 and 2 gears, this involves someone with STAR who knows the boxes to re adapt the torque converter lock up. I know that Colin at MBS is very good at this and I have been in two cars that he has set up and the changes were seamless and you never felt a thing.
     
  3. st4

    st4 Banned

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    It's to fix the harsh two into one shift. It can help but IMHO it's such a complex box missing parts like sprag clutches over the 5g box to smooth down changes. I never liked a single car I've driven with this box.
     
  4. television

    television Always remembered RIP

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    Steve the sprag clutch has noting to do with any gear changes, many of us have the 7g box and we are very happy with them..

    The sprag clutch on prevent the car from rolling back on hills in the C or W mode
     
  5. st4

    st4 Banned

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    are you sure?

    http://en.wikipedia.org/wiki/Sprag_clutch

    Automatic transmissions

    A sprag clutch is used in some automatic transmissions as a method of allowing the transmission to smoothly change gears under load. Various models of General Motors' turbo-hydramatic gearbox have used this system.

    A sprag clutch is used in most older automatic transmissions and some newer ones for shifts which require the synchronized engagement of one clutch with the disengagement of another. Using an overrunning clutch instead of a hydraulically actuated one makes this synchronization automatic. The sprag clutch simply "lets go" once the reaction force it provides is no longer needed. In a Simpson gearset, common to many automatics, this happens on the 1-2 shift, and reverses on the 2-1 downshift. The 2-3 shift is done by engaging a single clutch, and nothing is released. Some newer electronically controlled transmissions make "clutch to clutch" shifts, without any sprags.

    This can also be used exclusively in first gear (transmission shift lever in D, but auto valve body or management selecting 1st) on some autos. That way it will automatically provide forward drive, but will not provide any engine braking. This is done not so much to avoid engine braking per se, but rather to allow a low throttle opening 2-1 downshift as a car decelerates, to avoid a loud (and potentially abrupt) and unnerving jolt as a result of the downshift. On transmissions so equipped, manual selection of 1st gear typically engages an additional band that grips the same section as the one way clutch would engage, and thus allows for engine braking.
     
  6. television

    television Always remembered RIP

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    You should study the workings Steve of the 7g box, there is more than one way to skin a cat.

    The fact that adaption done correctly fixes most of these faults, and the fact that most of us have perfect changes shows that it is not needed,,, things do move forward with new ways of doing things
     
  7. st4

    st4 Banned

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    How come I have driven so many and I can detect that clunk in the box even when its fixed...

    Sometimes there is the correct way of doing things and why try and modernise and it is not so good.

    If it ain't broke, don't fix it.
     
  8. television

    television Always remembered RIP

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    This subject becomes boring Steve and you have no right at all to insist that my 7g is anything other than a delightful perfect box, the same as many others have told you.
     
  9. st4

    st4 Banned

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    I have every right to say my views about 7g, considering the range of vehicles I have driven with this box, and when we see a post requesting information about them, I will take the opportunity to post my views on the subject.

    That quite frankly, is that.
     
  10. drdre78

    drdre78 Senior Member

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    hi 7g box is good gearbox know but when it first came out it was terrible.
     
  11. st4

    st4 Banned

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    I've driven a 61 reg S class that clunks from 2nd into 1st, a 59 reg CLS that did it, an 09 C320cdi that did it, a 2009E500 coupe that was awful in every regard....

    Some people maybe are more akin to notice these things than others, but most of them I've driven do shift poorly in the lower gears.
     
  12. Jodel

    Jodel Senior Member

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    Exjag - If you are happy with the box at the moment, I'd leave well alone. I had a software update on my 7G done in March last year to fix a harsh shift from 2nd - 1st. This happened only when the box was cold, it was fine when warm. Apart from that, I thought the 7G box was excellent with very smooth predictable shifts and an uncanny knack of being in the right gear nearly all the time.

    Since the software upodate, the professional chauffeur has been replaced by a learner driver and the car has never been right since. It now lurches in stop / go traffic and you are in no doubt when it changes gear. It has been back to 2 main dealers and one indy to reset the adaptions in an attempt to restore the previously excellent performance - with only limited success. I can tolerate the car now, but it is not as good as it was or should be. Very few people seem to be able to set up these gearboxes correctly, so my advice would be to leave it alone and keep the dealer away from it.
     
  13. drdre78

    drdre78 Senior Member

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    well that the problems they started with when gearbox came out. Well if the box is bad don't buy it.If they have updated it and adapted it and still the same means never get rid of it. or try differnet dealer or
     
  14. st4

    st4 Banned

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    Buy a nice car with a 5g box. I did that....
     
  15. television

    television Always remembered RIP

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    And I bought a very nice 2007 CL with a super 7g box :D:D
     
  16. st4

    st4 Banned

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    I am glad you are happy with it....
     
  17. drdre78

    drdre78 Senior Member

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    ha there is two types of 7g gearbox you can tell by the sump of box
     
  18. st4

    st4 Banned

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    Theres 7g plus....

    It is supposed to be better.
     
  19. television

    television Always remembered RIP

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    Alex had a very nice 7g box in his R class
     
  20. television

    television Always remembered RIP

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    Colins first R class had a very nice 7g box
     

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