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Hey guys, what's the difference between AWD and 4WD in Subies? Mines a 89 Vortex with full time 4WD.
Canny

4WD is part time, range lever (or button/switch in autos) only to be engaged off road or on loose surfaces.

AWD is on all the time

This seems such a simple question - and it just so not .

here is some references

http://www.motoring.com.au/advice/2010/ ... An1R8P8HAQ

The question I always get wrong when trying to answer is - which subie system ( brumby 4WD with and without rear LSD, forester, vortex, wrx etc) does what when

1) one wheel loses traction

2) both wheels on the same axle loose traction

3) both wheels on the diagonal ( right front/left rear ) loose traction

4) three wheels loose traction.

My Vortex has full time 4wd, it's auto. There's no lever or button and no diff lock.

Vortex75 wrote:My Vortex has full time 4wd, it's auto. There's no lever or button and no diff lock.

So you have what is called AWD by rights

TOONGA

There are different types of AWD sytems. Correct me if I'm wrong, but I think the Vortex with full-time 4WD is an AWD system with a centre differential and a viscous coupling.

A 4WD system will lock the front and rear axles together, and can't be used on the road due to the speed difference between axles.

An AWD system delivers torque to both axles, but allows them to rotate at different speeds. This way it can be used on the road.

A true full-time 4WD system delivers torque to both axles at all times, allowing a speed difference, but can also be locked up.

Often you will see AWD systems labeled as full-time 4WD, especially in the 80s. The terms are sometimes used loosely.

When it comes to the all wheel drive trans in the Vortex I believe you have two beasts - depending on if it is manual or auto. The manual AWD box came with centre diff with a locking function for off road. The 4 speed electronic auto AWD has some ability to split the power front to back if I remember reading a motoring write up from the eighties

Yeah the 4 speed auto from both the Vortex and Liberty has 100% drive to the front wheels, and an electronically controlled hydraulic clutch to vary the torque sent to the rear wheels.

I don't think that's quite correct about being 100% to the front wheel normally.
I had a 93 Legacy GT auto (I know being an import & turbo it could be different from the normally ones) in the early 2000's, and I remember Honda doing a big ad campaign about their CRV being the first to offer that kind of system in the interests of saving fuel.
My Legacy had 60% front 40% rear normally & then would shift the drive rearwards as needed. Can't remember if it would do more than 50/50, but considering the way it would suddenly change to oversteer in the wet, it sure felt like it

The Honda CRV of many years ago that people thought was constant 4WD or AWD was, I believe FWD for normal driving, then, when sticky situations arose the double pump system in the rear diff would then activate the rear drive. I thought the sube AWD autos were something like a 60F 40 rear split in normal mode ...Neville know these inside and out in theory ??

Yeah should have clarified, I was referring to the MPT auto. The front drive is always 100% connected to the transmission, just the rear transfer that is variable

Turbo and H6 autos had VTD that was a planetarty 40/60 ( 41/59 in later models) split when open and variable up to 50/50 lock controlled by the TCU. Very much the same as DCCD in the STI manuals.

I don't know about the older AWD Subies like the Vortex, but the Forester, Lib/OB, etc has:
manual: viscous centre diff 40/60 - 60/40 fr/rr
auto: MPT pack centre 90/10 - 50/50 fr/rr

The manual is constantly varying torque, the auto only varies when the front loses grip.

I'm not so sure how the better auto with VDT works but I know its very effective offroad & locks the centre 50/50 when held in 1st & 2nd

Have a look at this.

It might be of interest for people in this thread...

Pedro.

pezimm wrote:Have a look at this.

It might be of interest for people in this thread...

Pedro.

Oh, um, how big is this ?

steptoe wrote:Oh, um, how big is this ?

5.2MB, sorry...

It's a PDF from Subaru Australia with details on multiple AWD systems of recent years.