All wheel or 4 wheel

snipped-for-privacy@webtv.net (Bob Miller) wrote in news:13193-3FFA593A-480 @storefull-2233.public.lawson.webtv.net:

Most AWD Scoobies these days are 90/10 meaning unless rear traction is needed, the vehicle is essentially a FWD. Its only re-distributed to true AWD under conditions that warrant it.

I believe the WRX and naturally STI are fulltime AWD but there are certainly people who are more versed in this that can add their 2 cents.

Close, Subaru has a couple of different AWD systems, Auto, Hydraulic fluid shift within the transfer case plates get pushed together 60/40 maximum split Electronic, disable with fuse when using small spare or AT temp light comes on.

5 speed Manual Viscous differential Coupling, plates separated by silicone gets thick and binds plates when heated, slipping 90/10 this is also used on the models which have Ltd slip rear's (XS and above Foresters, All Outbacks, but the sport, 2.5 GT, and WRX and STi.) STi also has an electronic suretrac system in the front.

VDC, Vehicle dynamics control, only on the VDC 6 Cyl OB, is an electronic system which will even depower 4 of the 6 cyl, can slow one wheel and speed up another. (only for the truly aggressive driver or for severe avoidance situations.) There is also a VTD, Variable Torque Distribution which routes

55 to the rear.

Now that should clear up the mechanics

AWD has an open center differential which allows for varying amounts of power, you are less likely to Hydroplane, you will track truer in the corners (4WD jumps in tight turns) it is better on the roads. 4WD is better off the Roads. When our plow truck gets stuck we pull it out with a Subie.

AWD is better for street driving in crappy weather. The main advantage you want over 2WD is that the torque on each drive wheel is 1/2, so you are less likely to lose traction, especially in corners. I have heard that in a 4WD you have to be careful going round tight corners in slippery conditions as the rear wheels are trying to go the same speed as the front (i.e. no center differential), so they spin out and you fish-tail. All Subaru AWD have some form of limited slip center differential so it helps too if you have one wheel or both wheels on an axel on ice.

4WD would be better in unplowed back country roads where you are not trying to go fast, just trying to go.

-- Dominic Richens | snipped-for-privacy@alumni.uottawa.ca "If you're not *outraged*, you're not paying attention!"

That would partially explain why my '87 XT 4wd crawls through deep snow better than my '92 Legacy AWD ! (narrower tires on the XT too).

jw milwaukee

Most "4WD" vehicles are part time, and if you're using them on snow on the road, it's to get unstuck, or to drive slowly. I'm sure it's fine for snowy conditions*, but AWD is more pleasant for on road driving.

Full time 4WD is very similar to AWD, but often (always?) comes with features that make it better for off-roading: 1. At least one locking diff 2. Low-range off-road gearing.

Full time 4WD tends to be only available on expensive trucks, although if memory serves, Kia may offer it too. OTOH, for nearly all of my driving, I think I'd rather be driving my Forester than a Kia Sorrento.

• (footnote) Last time I was in a vehicle that got stuck, it was a truck with a primitive PT 4WD system on an unploughed road. We were spinning one front and one back tire, and finally backed out (actually we continued on our bikes, then backed out after returning to the truck), since we couldn't procede. We had been chopping away fallen trees & branches to get as far as we did.

The truck may have had an advantage over my Sube as it had better clearance, but it's advantage sure wasn't in its drive system, as I have an LS rear diff, and should be able to spin 3 tires instead of 2. Also my tires are in better shape, which in this case I think mattered more than the drive system.

In my experience, it is about the same. An important point missed in this thread is that all Subies come with ABS. Also, this time of year in the northern hemisphere, most of the vehicles you see in ditches are 4WD. Stupid drivers do not understand that all vehicles have 4 wheel brakes and irregardless of drive do not stop faster ;( Frank

I always add the 4WB option. It's worth the money...

I don't mean to pick at what may be a typo, but what is a "4WB" option? I'm willing to learn something new!

4 wheel brakes, referring to the part below.

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And some does not understand that "all wheel" is identical to "4 wheel". Most vehicles have exactly four wheels.

"David" skrev i meddelandet news:btjuhh$81gpg$ snipped-for-privacy@ID-189417.news.uni-berlin.de...

Manufacturers mean different things by the terms though (although not that different). In neither case does a part-time system have a center differential. Although sometimes manufacturers and comsumers differ on what is and isn't a part-time system.

It helps to define the terms before making a decision on which is better. I didn't do that (although I may have clarified it a little in my first post), but I didn't say which is better either.

Okay, sorry. It was not nearly so naked in the earlier post. I see the humor now!