bobn3

Hi all,

I think this topic was cover before, but I cannot find the tread!

So.. What is the difference between AWD and 4WD, is it just the name or it is because you can change from two wheels to four wheels???

Any help,

Cheers

Ian Cook

Exactly the same, just 2 ways of saying it, All Wheel Drive and 4 Wheel Drive !

DavidRB

Unless you're driving a six-wheel buggy with drive to all six wheels.

[This message has been edited by DavidRB (edited 26-05-2000).]

DavidG

..or a Reliant Robin

MarkCSC

It has been put forward that an AWD car was designed to have 4 wheels driving the car all the time,(eg Subaru) and a 4WD car was designed to have just one set of wheels driving when it started out but they decided to convert it so that the other set of wheels put power down when traction was lost. eg Calibre Turbo 4x4 was a FWD car converted to 4WD. The rear wheels came in to play when there was a lack of grip at the front end.

Mark

Could be (and probably am) talking a load of poo but it is ten to six on a friday night and I'm still at work

[This message has been edited by Mark Champion (edited 26-05-2000).]

KevMac

I always thought AWD and 4WD were distinctly different.

Here’s my understanding of the different drives:

There’s the part-time 4WD like the Freelander’s and Honda CRV/HRV which only drives all the wheels when it gets slippy but basically they are front wheel drive.

Then there’s the heavy off-roaders like the Trooper, Discovery, Landcruiser where they have to use front wheel drive on the road because of their lack of rear diff.

Then there’s AWD like Subaru, Audi and Porsche where all the wheels are driven all of the time.

Am I totally mixed up?

Schwarzwalder

FWIW: In the States, 4WD was/is commonly used to denote systems which lack a center differential, have a multiple-speed transfer case, and cannot usually be used on dry pavement. AWD systems usually have no shiftable transfer case, have a center differential, and can be used on dry pavement. Now there are all kinds of new systems (full time 4WD, RealTime 4WD, etc)which are hybrids of both and can be used all conditions. The cost is, of course, weight and complexity.

Generally, here AWD is a lighter-duty system for passenger cars and 4WD is a heavy duty system for off-road use.

The definitions are blurring. Fortunately for my employer xWD is really catching on!

Frankie

The big difference between Subarus AWD and every other manufactuers 4WD is that Subaru do not use a transfer box, the drive for the front wheels is dealt with via a viscous coupling in the gearbox, this splits the drive 60% to the rear wheels ( rear drive is then distributed by an LSD)and 40% to the fronts, all other manufactuers use a gear box and a separate transfer box (which f**ks every thing up) this means that you get un- even weight distribution and a car ADAPTED to 4WD not DESIGNED for 4WD.Subarus system also allows near perfect linea drive as the engine and gearbox are mounted longdituanly rather than tranversly, allowing Subaru cars to use a Boxer engine and get the centre of gravity nice and low, which aids handling.
Right I'm going for a beer.....
Frankie

Doc

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by KevMac:
Then there’s the heavy off-roaders like the Trooper, Discovery, Landcruiser where they have to use front wheel drive on the road because of their lack of rear diff.

Am I totally mixed up?[/B]<HR></BLOCKQUOTE>

Afraid you are a bit mixed up. The discovery is permanent 4 wheel drive and certainly does have a rear differential as well as a front diff, a transfer box and a central viscous diff. The transmission is exactly the same as the classic range rover and I have changed the transmission oil enough times

Nir

I used to think the difference lies in the fact
that AWD distributes different torque to each wheel
according to road situation, while 4WD is simple 4x4.

Nir

Chris L

Doc

I reckon KevMac was referring to the Freelander which is not perm 4WD. On the road, it is basically FWD.