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A Drivetrain Question!


R W Burgess

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I have recently become a "all-wheel" drive small SUV owner (repo). Since we have been talking about suburbans and since most are 4 wheel drives, I am curious about the difference in "all-wheel" drive and "4-wheel" drive. Up to this point I have not owned either. I have on occasion seen all wheel drives on the roads, but since they are not common, I assume that they either did not catch on, or were not worth the trouble in the first place. Again, I assume that all-wheel is engaged at all times, with the attendant loss of fuel mileage.

Off road usages? Comments?

Wayne

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Wayne,

Unfortunately, most folks incorrectly use the terms "all wheel drive" and "four wheel drive" interchangeably. Technically, AWD is intended to be a full time system with a center differential and usually active control of the center and possibly the axle differentials. Audi pioneered the AWD with the Quattro coupe in the 1980s and invented a viscous center diff that used a special silicone fluid. Over the last few decades, AWD has become much more common than you think. Virtually all Subarus have it, as do all Audi cars with Quattro, the 4Matic VW cars, the iX BMWs, and many "soft-roader" SUVs. The Olds Bravada, for example, had a system called Smart Trak, with a computer controlled center diff. This was unique to the Bravada - the other S-truck based siblings from GM just had standard part-time 4WD at first.

When the Quattro first came out, Audi made a big deal of the fact that powering all four wheels was actually a handling benefit, even in dry conditions. How much of that is fact and how much is marketing depends on how cynical one is, however. ;)

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Wayne, Our old two wheel drive suburban was an incredible tow vehicle but would get stuck in wet grass. A lot of truck but not much in the way of grip off the pavement. I know this is not an answer to your question but just a little FYI. Several times -like the time I got the truck stuck in wet grass in the back yard and ended up having to call a tow truck to get my truck out of my own yard (flat by the way)- I wished I had the four wheel drive option.

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The Olds Bravada, for example, had a system called Smart Trak, with a computer controlled center diff. This was unique to the Bravada - the other S-truck based siblings from GM just had standard part-time 4WD at first.

How much of that is fact and how much is marketing depends on how cynical one is, however. ;)

Exactly the vehicle I have "inherited" Joe. ;) (1999 with 85,000 miles, just did an engine job. Previous owner had run it low on oil, spun a bearing:mad:)

The first word that hit me was "computer controlled"(ok, two words:)). My experience with older computer controls is not good, so that's a scary thing for me to read. Ok, I'm not going to keep this vehicle, just asking the question. I was wondering about the snow capabilties of the two different drivetrains though, and I'm sure that having 4 wheels "working" is better than two in bad conditions.

Thanks,

Wayne

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  • 3 weeks later...

I have an AWD Durango, Wayne, here in the snowy NE and my drive way is 750' long and up hill. The car has a switch that I can use to put it in 4 wheel drive. I've never needed it. Great traction and lousey mileage.......Bob

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I recently traded my 2005 Chevy Silverado 4WD for a 2007 GMC Yukon 4WD. I got and still get almost 20mpg from the 5.3L V8 engines in both running empty in 2WD. Both have vacuum actuated 4WD buttons that allow selections for 4WD Lo, Hi, or Automatic 4WD. The automatic feature is great when driving in questionable conditions on highways as 4WD (lock up) is not recommended on dry pavement where the tires cannot slip.

My wife has a 2007 Hyundi Santa Fe AWD with the upgraded V6 engine and gets only 22 mpg empty on the highway. It is a much smaller vehicle with little towing capability (doesn't even have a hitch).

Nuf said...?

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You would be surprised at how well an old 2 wheel drive truck can go through snow!

Let air out of the tires, add a pair of chains on the back wheels and throw a few hundred pounds of weight over the back axle. I know guys that plow lots like that and never get stuck in the snow.

Doesn't always take a lot of $ to make something work, just some ingenuity!

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You would be surprised at how well an old 2 wheel drive truck can go through snow!

Let air out of the tires,...

Do NOT lower the air pressure in modern radial tires. Just ask Ford and Firestone how low tire pressure worked out for them on the Explorer. It will not increase traction and it will lead to handling problems and excessive tire wear.

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Well, I have gotten the Bravada back from the body shop (replaced the right hand mirror, had the guy reattach the inside door panel pockets (wonder if these automotive gurus ever thought that plastic pieces may split apart from too many maps, napkins, bottles, etc?:))

At least it runs and drives ok, vibrates a bit, makes me think a universal joint may be in question. As usual, Wayne will drive it until it gets bad enough to find out where the problem is (wheel falls off?:D)

Can't wait for the first snow storm to try her out. Darn shame it wasn't below freezing this week. Let's see 12 inches rain by 1 foot of snow???? :eek:

Yes, that would have done just perfectly. Wait! What am I saying, I hate snow! :cool:

Wayne

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