Since you are on the topic of AWD vs 4WD... I want to post something that Frost has posted elsewhere about the same issue...
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For some bloody reason, people are still very much confused about the rather large differences between All-Wheel-Drive (AWD) and Four-Wheel-Drive (4WD - this includes both part time, full-time, Nissan's ATTESA, Honda's stupid Real Time).
Here's the perfect article by Graeme Fletcher, a respected journalist and wheel-head. You've seen him on the Motoring 2004 series on TSN and his credentials speak for themselves.
The difference between four- and all-wheel drive
By Graeme Fletcher - National Post
Friday, May 07, 2004
The key advantage to driving all four wheels is the added ability it can impart to the vehicle. Rather than having to push 50% of the horsepower and torque through each of the front or rear wheels, the system divides the power among all four. This not only reduces unwanted wheelspin, it improves traction on wet pavement and loose surfaces and, perhaps more importantly, whenever traction is temporarily compromised -- such as encountering debris (sand and the like) or a slick spot (oil or ice) on the road.
This description applies to both four- and all-wheel-drive systems. However, this is where the confusion tends to come into play, simply because the terms are bandied about with little or no regard for the significant differences between one system and another. Four- and all-wheel drive are best differentiated according to whether or not the system has a low-range gear set -- in my book, four-wheel drive does; all-wheel drive does not.
Four-wheel drive is generally used on SUVs and pickup trucks, and can be split into two very different groups -- part-time and full-time. The former is exactly as described -- part-time in that it is to be used only on a slippery surface, which is not very much of the time because engaging it on a dry, high-traction surface can cause damage to the drivetrain.
Locking the centre differential (which happens whenever the system is engaged) prevents the rotational speed differences between the front and rear axles (caused by cornering) from being dissipated and so the drivetrain begins to wind up. Driving a part-time system in a circle on dry pavement when engaged causes the vehicle to buck as it tries to spin off the windup by breaking loose one or more of the wheels.
Part-time systems also entail driver input to activate, which further compromises its effectiveness. For example, most highways are ploughed and free from snow during winter. However, many off-ramps are still slippery and so the part-time system must be activated and deactivated according to the changing conditions. The problem with this is that the action invariably comes too late to be of any real benefit, as all part-time systems have a speed above which they cannot be engaged -- some as low as 40 kilometres an hour, which is just too slow to be of value in the off-ramp scenario.
A full-time four-wheel-drive system can be engaged on a dry surface and usually includes an automatic mode. However, most only drive one set of wheels until they begin to slip, at which point the system automatically begins to transfer some of the power to the other wheels. Typically, these systems are referred to as on-demand systems. While of value on a slippery hill or ploughing through snow, they tend not to add to the dynamic ability of the vehicle. This is what separates the on-demand types from true all-wheel-drive systems.
Consider an on-demand system that only drives the front wheels until they begin to slip. In a corner, the vehicle tends to understeer when the front wheels lose grip. Now, shifting some of the drive rearward momentarily pushes the vehicle further into the understeer condition until the front wheels regain grip. That can be scary.
Conversely, the all-wheel-drive systems employed in the new Subaru Legacy power both the front and rear wheels all the time. In most cases, this means sending more power to one set than the other. Depending upon the model, the manner in which this is accomplished varies -- the system tied to the manual transmission is good (it uses a viscous couple to accomplish the power transfer); the one tied to the automatic box is better -- simply because it is more progressive and proactive, which means more balanced.
In the base Legacy, the system married to the automatic uses an electronically controlled clutch pack to distribute the power between the front and rear wheels. Normally, it sends 60% to the front wheels and 40% to the rear. This brings two advantages: First, the extra weight over the front wheels (about 60% because of the engine and transmission) makes it possible to fire more power through them than to the rear wheels before wheelspin becomes an issue. In essence, the weight bias cancels out the drive bias, giving an effective 50/50 split. If any of the wheels do spin, the centre differential locks to deliver a real-time 50/50 split. The second bit is more about preference than ability, as it allows the car to understeer at the edge of the traction limit, which is less disconcerting than oversteer to most drivers.
The system employed in the range-topping GT is better if you want a truly engaging drive. Under normal circumstances, the system sends 45% of the power to the front wheels and 55% to the rear, which imparts a sportier feel because it is possible to hang the tail out. It can lock the differential to split the power evenly if that's the best strategy. But this is the proactive part -- mat the gas and the system recognizes the urgency and automatically locks the system to prevent the back end from fishtailing. Once up to speed, it relaxes its hold, which allows the driver to hang the rear end out. It only intrudes when the driver steps beyond his ability -- my sobering moment came half way around the Cabot Trail in the midst of a torrential downpour.
Regardless of the type, the Legacy's handling is helped by the fact that all of the systems Subaru employs are symmetrical about the centre line of the car. This balances the weight left to right (many are forced to offset the weight in order to package the system) and allows the use of equal-length drive shafts, which banishes torque steer; this in spite of the GT's 250 pound-feet of torque.
<End of article>
For those of you who've read my other explanations, you'll realise I've been saying exactly what Mr. Fletcher here has just said. I have not tried out nor know much about the system in use for Volvo's AWD systems but from initial research, I hear under normal circumstances, the car will have 99% power to the front 2 wheels. Again, I seriously dislike this idea for the same reasons Mr. Fletcher said. The perfect AWD car for daily driving in my mind, would be a 50-50 final bias (drive AND weight combined). This means that in the case that I DO lose traction on any 2 wheels (front pair or rear pair), I have at least 50% power on the road at THE INSTANT OF TRACTION LOSS. For the system by Volvo, if I lose traction in the rear, no problem, it should have 99% power upfront. But how often do you run into situations where your rear loses traction before the front in normal driving conditions? Rarely. Normally your front goes out (simply because it is the FRONT and your car drives FORWARDS into any territory). So say I run into an ice patch. At the INSTANT I hit the patch, the car has 1% power delivery AT THAT INSTANT. While this may be for only 0.001 seconds or what not, the car still has to respond considerably before 50% of the power is diverted to the rear. Also, by suddenly sending most of the power to the back where it normally is almost never present, we are effectively switching cars on the driver. The car will behave differently and the driver will attempt to compensate which in turn will make the car compensate which in turn will make the driver compensate which in turn will... you get the idea. Even Mr. Fletcher agrees on this.
By having a 50-50 split (final), when I hit an ice patch, at THAT INSTANT, I have 50% power to the rear, which means that the car will feel 'weaker' (in sense of acceleration vs. amount of gas pedal pushed in). Let's assume this perfect AWD car can send up to 99% to the rear, it is still only a +49% increase from normal situations as opposed to the +98% increase by Volvo's system. That is HALF the power that is sent to the rear compared to the Volvo! This means that the sudden extra power in the rear will not affect the driver as greatly as Volvo's system does which goes back to the point of driver-car-driver-car compensation loop.
Generally, I dislike how the AWD name is being haphazardly tagged onto vehicles that really should not be tagged by such a name. I believe Volvo is making a serious mistake in doing so but who am I to argue against the mighty corp?
Anyways, I hope you all learned something. Cuz I'm sick of explaining it to everyone, especially the so-called EVO or WRX / STi experts who don't know shit about AWD and 4WD systems yet can still call themselves experts.
Frost
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Finshed 
. Reason being as a 4wd Cannot be driven on dry roads or any road infact without putting great strane on the Gear box.
u sure about that? 
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