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How it Works! Welcome to Auto 101

This is for newbies and experts alike. If you don't know the basics about cars (or forgotten them) this is the place to find out. Even if you have more technical questions, post it here!

This topic is meant to run the technical gamut. Anything from how to change a flat to how to rebuild an engine. From what tire treads are for to what the heck a k-body type car is.

Just remember that there are non-engineers and newbies (like me) out there, so please try to use plain ol' English whenever possible (especially for the lurkers out there ;>). Thanks!!!


  • pocahontaspocahontas Posts: 802
    Hi jusdreamin- Good topic! Thanks for starting up this new disscussion.

    To everyone- As I mentioned above, this discussion is linked to both the Women's Auto Center and the Maintenance & Repair message boards. This means you have the option to access this discussion from either one of these message boards.

    Hope you enjoy discussing this subject with the participants from both of these message boards. Thanks for your participation! ;-)

    Hatchbacks / Station Wagons / Women's Auto Center Boards

  • mfarmer2mfarmer2 Posts: 67
    I just bought a front wheel drive Buick Rendezvous with the "full range" traction control option. Not really sure what that means, except for that it helps control the vehicle better. Can someone explain to me how "full range" traction control works?

    Also how does traction control differ from all wheel drive? Please use the simplest terms; I tried reading an article on the subject and was still did not quite get it. Thanks ahead of time for any feedback. :-)

  • What are the differences between AWD, FWD, RWD, and 4WD? Why would someone want one over the others?
  • I think traction control transfers the power from the wheels that slip to the wheels that grip.

    AWD is similar to 4WD. The difference is that you can turn off 4WD if you don't need it.

    I think the best way to put it is that both AWD and 4WD have all four wheels "gripping" the road. I'm rephrasing what I said earlier to clarify here: AWD has all four wheels constantly "gripping" the road.

    AWD tends to get worse mileage and wear out tires quicker.

    I didn't realize that there was "full range" TC. Could that be a marketing ploy?
  • pocahontaspocahontas Posts: 802
    In addition to the feedback here, you may also want to check out these articles from Edmunds Ownership Section: What Wheel Drive?, By Karl Bruer and Traction Control, by Scott Memmer. Do these help to answer some of your questions?

    Perhaps someone else has more to add.... ;-)

    Hatchbacks / Station Wagons / Women's Auto Center Boards
  • 0patience0patience Posts: 1,542
    AWD (All Wheel Drive) - All wheels are powered fulltime, There are good and bad points to all wheel drive.

    RWD (Rear Wheel Drive) - Up until the 70s, was pretty much the exclusive design, with exception of the Tornado and a few imports. Control can suffer becasue of the "push" that it has on the vehicle. But it is my personal preferance.

    FWD (Front Wheel Drive) - Has been said that it has better control over rear wheel drive, because the power is pulling the vehicle in the directions that the tires are pointed.

    4x4 - 4 Wheel srive, comes in full time (Some are a partial part time) or part time.
    Full time, is setup where the hubs are locked constantly, and the 4 wheel drive is engaged. Some full time, have the hubs locked and you still have control over whether it is in 2WD or 4x4. Part time has hubs that can be locked or unlocked and usually have 4 Low, 4 high and 2 high capabilities.

    Full range traction control - Is not really any of them. Designed to put the power to the wheels that the computer sees that needs it. If one tire starts to lose traction, the computer (loosely termed) will sense the traction loss and shift the power to another tire. While this is a pretty good system, it can be extremely expensive should a problem come about.

    jusdreamin, You wrote;
    has all four wheels constantly "gripping" the road.
    That is not accurate. Any of the drives put power to the wheels, it cares less if the are gripping or not and often at least one of them are NOT gripping the road. Esecially 4x4 and AWD. At any time in a corner or turn, under power or acceleration, there is at least one tire not "gripping" the road.
  • Thanks. Well, at least in essence I got the traction control right.

    I thought the WD's did have something to do with power, I just couldn't remember it. Yeah... that's it... I couldn't remember. :)
  • Also keep in mind that "grip" is related solely and ONLY to the tires, as Opatience implies. You can have 40 wheel-drive, or even tank treads, and you'll go off the road if there is no "grip".

    Many an AWD or 4X4 driver has learned the hard way not to be overconfident in an "all-wheel drive" vehicle.

    Your car or truck stays on the road only because of those 4 little tire footprints, amounting to only a handful of square inches of tire patch.
  • Stever@EdmundsStever@Edmunds YooperlandPosts: 38,926
    The 4WD & AWD systems explained discussion may also be of interest.

    Vans, SUVs and Aftermarket & Accessories Message Boards

  • Thanks!!

    Does anybody know what curb weight is and why is it important?
  • Curb weight is the net weight of the vehicle. The car with a full fuel tank and no passengers or cargo.
  • zueslewiszueslewis Posts: 2,353
    the way I've always explained traction control is that it is just the opposite of anti-lock braking and frequently uses the same sensors to control the system.

    With ABS, sensors "sense" pending lock up of your wheels during hard braking and you get the best braking ability when the wheels are turning slowly instead of skidding. That's why you can steer (and actually have it work) when "panic" braking with an ABS-equipped car.

    With traction control, the sensors keep your wheels from spinning, slowing things down so your tires can work with a slippery surface instead of sliding over it.

    Curb weight - very important when adding weight of your cargo to make sure you don't exceed "gross vehicle weight" or GVW. Also good to know if you're driving over old wooden bridges!
  • I know that this is an oversimplification, but I use this in conjunction with horsepower (or torque) to get a very rough estimate of the (relative) acceleration power of a vehicle.

    As an example take a 01 Honda Acccord LX V6 automatic (curb weight/hp)
    3274/200 ~ 16.4
    vs. a 01 Acura 3.2 TL w/nav automatic
    3508/225 ~ 15.6

    I would (very) roughly expect the vehicle with the lower amount of weight per horsepower to have the better acceleration.
  • All other things being equal, probably that's true. But if there were variances in tires, differential/transaxle gearing or even (at higher speeds) aerodynamics, your formula might not hold true.
  • Mr Shiftright, I agree that there are many other factors are not considered such as hp vs rpm, load distribution (e.g. FWD with 60% of weight on front axle), addition of driver/passenger weight, etc. Also, actual vs rated.

    Very rough estimate. Did I mention that it is very rough? :~)
  • Oh, okay, this is THEORETICAL physics we are talking it!
  • That's NOT theoretical physics!! Theoretical physists don't beleive in numbers, therefore theoretical physics DOESN'T involve them!!!

    I found that out the hard way...:)

    Hmm...Would "under ideal conditions" be more appropriate?
  • What components are covered under the "Power Train Warranty"? What should I know about this type of warranty when shopping for a new car? Is a 10yr/100,000mi much more desirable than a 3yr/36,000mi? Or will I ever really need it?
  • zueslewiszueslewis Posts: 2,353
    The powertrain warranty USUALLY (very few exceptions) describes defects with the INTERNAL portions of the engine, transmission/transaxle and the axle shafts. The powertrain warranty does not cover adjacent components like all the electronic control devices that tell the powertrain how to act. There are at least three major control modules, two major wiring harnesses and gillions of sensors involved in the powertrain that are NOT covered by most powertrain warranties. Only the basic warranty covers these items, but the 5 year/5000 or 10 year/10000 mile P/T warranties sound good as a sales technique. 5 years roadside assistance? Why should a manufacturer feel compelled to make these promises if they weren't NECESSARY? Scary, huh?

    My main point is that the electrical components that may fail at 50,000 miles are very expensive and not covered by the P/T warranty.
  • You may also want to read this Edmunds' article about Warranty and Roadside Assistance Coverage. As mentioned here, the Drive Train (a.k.a. power train) warranty "takes care of most of the parts that make the car move, like the engine, transmission, drive axles and driveshaft."

    These are major components than can be can be very expensive to repair. So imo, a 10 year powertrain may certainly come in handy, especially with certain makes/models (I won't mention specifics); you can refer to Edmunds' new and used car guides for basic overview and reliability information.

    Zueslewis also makes a good point about adjacent components (i.e control modules/major wiring) not being covered on many manufacturer's power train warranties, only on the basic warranty. Not a bad idea to check with the specific manufacturer or dealer to find out exactly what is covered in their basic & power train warranty. Good luck. ;-)

    Hatchbacks / Station Wagons / Women's Auto Center Boards
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