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Most mechanically complex component of an automobile?

  1. Aug 22, 2011 #1
    What is the most mechanically complex component of an automobile? Someone told me that an automatic transmission is more complex than an electronic microchip.

    I do know a tiny bit about auto mechanics, but not much. Manual transmissions are relatively simple, mechanically. It's called gear ratios.

    Back 30 years ago, the mechanics in automobiles were very basic and simple, and if you had the proper tools and technical know-how you could perform most of the repairs yourself. But today, it is almost imperative you take your vehicle to a professional repair shot to have it fixed.

    With today's vehicles, you have to have a degree in electronic engineering to repair one yourself. There are more chips in a modern car than there are in the computer I'm using.
  2. jcsd
  3. Aug 22, 2011 #2


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    Complexity isn't easily defined. I'd propose a mechanical fuel injection pump or similar.
  4. Aug 22, 2011 #3
    Although automatic transmissions are extremely complex and difficult to engineer.


  5. Aug 22, 2011 #4

    Ranger Mike

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    id have to say the new computer systems that now control all the fuel/air mix, throttle position indicator, EGR sensor and the like..automatic trans is no problem if you take your time and follow the fluid path and understand basic fluid dynamics..its just looks complex and intimidating..but the crap they put out now means you can't work on the car unless you got a computer interface, know the error codes and can run diagnostics..
  6. Aug 22, 2011 #5
    These cars did not need computers and electronics to repair. Just metal tools and a garage.

  7. Aug 22, 2011 #6
    I'd say a transmission, especially the new 8 speed semi-automatic transmissions like on the Lexus IS F.

    [PLAIN]http://upload.wikimedia.org/wikipedia/en/f/f9/Automatic_transmission_cut.jpg [Broken]
    Last edited by a moderator: May 5, 2017
  8. Aug 23, 2011 #7
    Nothing mechanical is really that complex when you dig down to the individual components. Also define complex: amount of bits in the system, complexity of operation, engineering required etc?

    However, to answer the question.
    Limited slip diffs.
  9. Aug 23, 2011 #8
    Some gears and a clutch mechanism?
  10. Aug 23, 2011 #9
    Active LSD are black magic (quite qute as much as aero or tyres though).
  11. Aug 23, 2011 #10

    Ranger Mike

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    yeah Chris...to tune it right (Limited slip diff) is a bear...thats one reason round trackers use spools...auto trans is pretty trick too...but as Mender said.. still parts is parts and not too bad to learn how to trick them up...
  12. Aug 23, 2011 #11
    Pharmaceutical or mechanical?:wink:

    Mechanically they're still fairly straightforward; as in EFI it's the programming that gets complex. I'm assuming you're including traction and skid control; yes?
  13. Aug 23, 2011 #12

    Ranger Mike

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    Nooooooo..that would be illegal....like nitrous ...dont know a thing about these...
  14. Aug 23, 2011 #13
    Mechanically they are fairly simple, but even a passive LSD requires hefty engineering. The interaction and progressive nature is more complex than the way any old gearbox works.

    It's like I said, when you boil down any machine, what each component does is actually very simple. It's the interactions that make it complex.
  15. Aug 23, 2011 #14
    The J1939 CAN bus network that all the electrical components use to communicate. That is my vote.
  16. Aug 23, 2011 #15
    But the question is:
    Given that most people can't correctly describe how a torque converter works or even how to calculate the various ratios available with a planetary gearset let alone the flow chart for a typical valve body, my vote is also the automatic transmission.

    But as Chris said, the definition of complex is needed.
    Last edited: Aug 23, 2011
  17. Aug 23, 2011 #16


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    My Honda Ridgeline and my wife's Subaru Forester both have full-time AWD with traction-control and active stability-control (anti-skid). I'd really hate to have to trouble-shoot any of those systems. I have always worked on my own motorcycles, but cars and trucks have gotten away from me in the past 20 years or so, apart from basic maintenance.
  18. Aug 24, 2011 #17

    Ranger Mike

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  19. Aug 24, 2011 #18
    To properly troubleshoot these, one must know what the engineer(s) programmed the control unit to do in response to readings from the various sensors. Without that info you're shooting in the dark.

    One customer at the M-B dealership that I worked at had a 4matic E320 (ABS, traction control, ESP) that responded properly but at a much slower rate than it should have. I spent way too much time on the tech line trying to get the info needed to fix it. Over the course of a winter, all the major components and software were replaced or updated under warranty without solving the issue. I suspect that a faulty sensor in another subsystem feeding through the CAN bus network was responsible, or the network itself - but I apparently wasn't cleared for that level of info.

    The system itself isn't very complex; a set of solenoids modulating hydraulic pressure from the ABS pump to the appropriate brake caliper(s) but the processing of the sensor readouts to decide which solenoids to operate and for how long certainly can be.
    Last edited: Aug 24, 2011
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