Hey guys,

I was talking to a few blokes at work and we couldn't work out the difference between AWD and 4x4?
Is it to do with the differential? Or the size of the vehicle? Or power distribution?

I'd love it if someone could help me out

Cheers, Ollie

As described by Alan Swanson


Full-time 4WD operates as the name suggests. At all times torque is supplied to all four wheels, all of the time. The driver usually has several options available to them which affect the operation of the drivetrain depending on the conditions that are encountered.

In normal operation (such as driving on a bitumen surface) the front and rear axles are split by a differential which allows them to operate at different speeds when required -- for example, when cornering.

In most vehicles there will be the option of 'diff lock'. This locks up the centre differential and restricts any rotational difference between the front and rear axles. It's a feature that is commonly used when offroading to gain maximum traction.

There may also be the option of 'low range'. Usually used in extreme offroad conditions and on steep inclines, this changes the gearing of the drivetrain to provide a torque multiplying effect similar to the lowest gearing on a mountain bike.

Part-time 4WD is the original 4WD system and the most basic.

As with Full time 4WD there are several options available to the driver. In normal conditions the vehicle is driven in two-wheel drive, usually powering only the rear wheels. 4WD mode can be selected either by a separate mechanical lever or by an electronic switching system.

When 4WD is selected, torque is split evenly between the four wheels.

Part time 4WD vehicles tend not to have differentials between the front and rear axles. This limits the use of 4WD to offroad use because use of this feature on bitumen surfaces (where tyres have good traction) can cause excess stress and damage to the drivetrain (often called wind-up).

Most vehicles of this type have the option of 'low range' for extreme off-road conditions.

All-Wheel Drive is in some ways similar to the full-time 4WD system in that it also sends torque to all four wheels constantly.

These systems never have the option to operate in two-wheel drive, and unlike the 4WD systems, the differential between the front and rear axles cannot be locked. The differentials do, however, have ability to limit slippage between the axles if a low traction situation is encountered.

Usually this ability is provided with a differential known as a viscous coupling although more recently a similar outcome has been achieved by using electronically-controlled hydraulic or electro-magnetic 'clutch' systems.

AWD systems also lack the 'low range' feature which is common in most 4WDs.

The AWD system is less effective and more fragile than the 4WD system in a situation where high torque is required. Indeed, the viscous coupling units simply cannot satisfy high torque demands when the vehicle is offroad. AWD vehicles tend to be more 'car' like than obvious offroaders.

4wd is serious AWD is a gimmick... That said most people wont put themselves into a situation in the $60-80K AWD cars to warrant a propper 4wd system. propper 4wds are strong robust and able to handle serious terrain, and get you out of trouble. Again the car is sutup that way. Have a look at the tyres for example, who would go serious 4WDing with quiet and smooth highway tyres????
Depends what you are looking for.

http://www.youtube.com/watch?v=rgdExdKxIyE&NR=1 

4WD & AWD

http://www.youtube.com/watch?v=W4IYYOYfgig 

Thanks Jace, appreciate that

Still a little foggy to me but I think the line,

"These systems never have the option to operate in two-wheel drive, and unlike the 4WD systems, the differential between the front and rear axles cannot be locked. The differentials do, however, have ability to limit slippage between the axles if a low traction situation is encountered."

best sums up the difference!

I'll have to view those youtube clips at home - at work at the moment!

Thanks Guys!

My understanding is that 4WD is what is typically used in vehicles intended for off-road use e.g. Landcruisers, Patrols etc. Most have either manual or automatically locked front hubs. When you are on tarmac the front hubs are unlocked and torque is sent to the rear wheels only, when off-road the front hubs are locked and torque is sent to all four wheels.

All wheel drive is what typically found on cars intended for on-road use - Subarus are probably the best known example. Torque is sent to all fours wheels in accordance with how much grip each wheel has. Less grip, less torque, more grip, more torque.

Have a look here: http://www.subaru-global.com/about/awd/performance/index.html

awd = diahatsu terios
4x4 = landcruiser

Which one would win a jousting competition? Definitely the landcruiser

if a 4x4 like a landcruiser is set in 4x4 mode, then it pretty much is awd. i was under the assumption the only reason for going to 2wd in a 4x4 was simply for fuel economy to reduce drive train losses in power.

The viscous coupling set up on a T25 is an AWD system(like Quatro).A syncro with a decoupler becomes selectable AWD as it can be driven in 2WD then switched to AWD on the fly.(with speed).
If someone was to replace their VC with a solid shaft,then there Syncro would become 4WD and couldnt be driven on pavement whilst decoupler was coupled.

A 4WD could drive over the top of an AWD. But only if the 4WD could catch the AWD

baaah. If its all wheel drive and it has 4 wheels then its 4 wheel drive. Trying to put them into different boxes is just a marketing exercise.

Awsome Audi vids!

Awsome Audi vids!

I was talking about this with the offroad nutter at work last week. The common consensus is that a lockable centre diff is what makes it a real (ie offroad creek crawling etc) 4wd.

Sorry Mick, but ^^^ that's not correct either. Even a 'true 4wd' won't go anywhere if you jack one wheel off the ground, only one with a locked center diff will do that.


I'm with the marketing bs being the difference !!!

Yeah, big old boxy 70 or 80 series landcruiser

I remember watching the boss "test" the 4wd system on the audi TT quattro system in the workshop. Dump the clutch and the front wheels would do about a full revolution from memory before the haldex unit would send some power to the back and it would drive off.

http://www.4x4abc.com/4WD101/awd.html 

Notice down the bottom the T3 gets an honorable exception

At the end of the day it doesn't matter if you've got 4,2,1WD or have to push the car, unless you have enough ground clearance the car wont go very far off road!!

Quote:

Originally posted by SuperOwen http://www.4x4abc.com/4WD101/awd.html  Notice down the bottom the T3 gets an honorable exception At the end of the day it doesn't matter if you've got 4,2,1WD or have to push the car, unless you have enough ground clearance the car wont go very far off road!!

http://www.youtube.com/watch?v=bU6zEO6Z2ZA 

Thats funny.....

The new VW AMAROK has a choice between 2WD, full time 4WD, or part time 4WD with low-range. All available with rear diff lock. Something for everyone........
I was under the impression that an AWD normally receives its power to either the front wheels ( ie; vw transporter,honda crv ) or rear wheels ( ie; ford territory ) UNTIL WHEEL SLIP IS DETECTED then the power is sent electronically or mechanically (syncro) to the opposite diff. A cross axle diff lock is one of the most important off-road devices whether in a 2WD AWD or 4WD. I have experienced bogged traditional 4wds ( cruiser,patrol,landrover) its the same old story one front wheel spinning, one rear wheel spinning and going nowhere...............just to confuse everyone further some 4WD owners tell you their beast has a diff lock but it usually is a CENTRE diff lock not a CROSS AXLE diff lock............... ohhh it just goes on and on and on.............

Hmmmm.....not correct. A T25 Syncro is a FULL TIME 4WD,the coupling only changes the amount of torque/power applied to the front differential. To determin the difference between AWD and 4WD - there IS a big difference- is easy....jack up one back wheel,the car will not drive off if it is a AWD vehicle, a true 4WD vehicle will drive off powered by the front wheels...



If a VC has gone aggressive then it will drive the front wheels.If it is functioning properly and there is no difference in rear and front wheel speed then there should be no torque applied to the front,Is this not correct?
Most VCs go aggressive causing driveline damage during tight pavement turning.If a decoupler is fitted then you can decouple whilst turning so you dont do damage.
I know other things will play a factor in this,tyre wear,road camber etc which makes the front drive.
Some people opt to replace their aggressive or passive VC with a solid shaft.You then definatley need a decoupler and cannot drive on the pavement whilst all four wheels are driving.I would consider this as a 4WD vehicle.