LSD

[andyhui01]

but what if it has an adjustable c.diff like the new Impreza or Impreza RA's?.. they are still AWD vehicles but the driver can manual adjust the diff when needed.... and doesn't the Evo have a center diff as well?... even though it isn't AWD

 

[snars]

That's why he wrote AWD and 4WD. There's a difference between them.

Greetz Johan

My point was: there are cars with a transfer case AND a center diff (like the Defender, Discovery, later Toyo Landcruisers). Secondly, there are lots of AWD cars that lack a differential but employ some sort of coupling instead of gears. So that really disproves his statement '4WD cars have a transfer case, AWD cars have a center diff' . See?

 

[Cubits]

How about this.

AWD dynamically distributes torque fore/aft upon need, while 4wd has a fixed torque split.

 

[andyhui01]

AWD dynamically distributes torque fore/aft upon need, while 4wd has a fixed torque split.p

isn't it the other way around?... AWD like Subaru's have locked torque split... well except for Spec-C's subaru's and STi's.... and 4wd distributes upon need like the Evo, skyline......

 

[YipMing]

who cares
those terms are thrown around too much now adays
blame it on PR and marketing ... so let's just drop it

To me, 4wd tends more to refer to cars that goes offroad. Landcruiser, Pajero, Discovery, whatever, those jacked up wagons with big wheels that goes offroad.
And AWD tends to be for cars that use it for sport or safety or other reason. Like Subarus, Quattros, Evos, Skyline GT-R, etc etc ...

Let's just say that both have the ability to somewhat transfer power to all four wheel at once okay?

Peace

 

[andyhui01]

lol... I have to correct you slightly... AFAIK, AWD means that the power that is split to the front and back is 50:50... wherelese 4WD can be any number

 

[Leppy]

hmm I always thought of 4WD being something you didn't use all the time. Like the old Subaru Brumby's have 4WD/2WD but you wouldn't use 4WD mode on the road or you'd break a drive shaft.

 

[Cubits]

No, that is part time 4wd.

When you turn, the front/rear wheels rotate at different speeds. A part time 4wd locks the front and rear axles together (essentially), so there is no way to dissipate this difference. Something gives unless you're offroad, in which case wheels will spin to compensate.

Full time 4wd has a centre diff which takes care of that. Some 4wd's have smart part time 4wd, like the pajero, which has a lockable centre diff. It does the best of both worlds, allowing 2wd or 4wd on any surface, with the option for serious offroading by locking the centre diff.

An AWD will redistribute torque when a wheel slips. Even though the base distribution may be 50:50, when something spins torque will move away from it. That was the basis of a LOT of subaru ads. Their symmetrical ads are about the left/right distribution of torque, because the engine is mounted longitudinally, unlike many of it's compeditors.

 

[snars]

who cares
those terms are thrown around too much now adays
blame it on PR and marketing ... so let's just drop it

Agreed. Sorry guys, but there is no fixed definition for 4wd/4x4/AWD etc. Let's just say there are lots of different fourwheeldrive configurations, with different characteristics and purposes. They all serve to drive 4 wheels instead of 2.

You can't compare them by the names the marketing guys came up with. Do your homework before you start yappin. I'd really rather know what configuration of parts is actually driving the car than what the badge on the boot is saying.

 

[freerider]

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

They do mean something. But this doesn't mean that there aren't any differences inside each type. And yes, the terms are often wrongly used, but that's also because most people don't know there's a difference.

Greetz Johan

 

[snars]

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

They do mean something. But this doesn't mean that there aren't any differences inside each type. And yes, the terms are often wrongly used, but that's also because most people don't know there's a difference.

Nice site. I was almost ready to start bitching about his comments on viscous-coupling AWD systems, because my VW syncro bus can and will kick ass offroad but then I read this:

An honorable exception from the rule "AWD is almost useless beyond pavement" are VW Sycro Vangon. Yes they have viscous couplings to distribute torque front/rear - but they have a granny low first gear and they have axle diff locks (real diff locks!). So, they are much more capable than most folks think.

Phew.. :lol: