Awd percentage

[Sub Zero]

Hey guys so me and a workmates were discussing this and we couldn't figure it out so I've got a 2007 subaru legacy sedan and we were wondering what is the power percentage of the wheels like is it 50/50 or is it different? And also when you have a 4x4 and you push diff lock is it locking all 4 wheels so they have the same amount and can't slip?

Cheers

[ADIKT]

Pretty sure they are mostly FWD in normal driving conditions - trying to find out where I found this info (researched a while ago when I couldnt get my bl5 up a grassy hill)

[Sub Zero]

Yeh I couldn't find any info about it but I might have been searching the wrong things

[GC8E2DD]

The viscous centres are 50/50.

[Sub Zero]

So they are 50/50 then?

[Guest]

Some **** about the torque split is more rear focused. Couldnt get my head around it.

[Andy_Mac]

Assuming they used the same idea in older models. Seems to be 50:50 for the viscous centre in the manuals, not quite as straightforward for the auto's though

http://www.subaru-global.com/tec_awd.html

[Joker]

/ 70/30 to the front usually on autos & such like i thought

[DRFVDR]

the Manuals with the Viscous is 50/50

The Autos can vary 90/10 thru to 50/50

When you lock the centre diff/trasfercase in a "real" 4wd you get 50/50

[Joker]

oh yea the AWD vs 4wd debate heh

Subaru's are AWD NOT 4WD

[Guest]

Sure bc5ra knows.

[Sub Zero]

Ok so the manuals are more 50/50 and the autos can vary depending on model and year I would think?

And yeh I know subies are awd not proper 4wd haha. It's quite interesting to see that the autos are different tho.

[GC8E2DD]

What is your definition of a 'proper 4wd'?

[Joker]

transfer case

60 front 40 rear 30 fun

[GC8E2DD]

A centre differential (or more pedantically the housing) essentially /is/ a transfer case right? Either way, that is a horribly ambiguous way to define a 'proper 4wd'.

[Marky]

I know this is a can of worms to open but surely AWD is just a marketing term

Nissans get labelled 4x4 and they work the same way with electronic diff inside the gearbox

Late model mitsi's have the centre diff in an external transfer case so does that make it 4wd

For what its worth the autos are FWD with an electronic centre diff able to at most take 50% of that power away

DCCD cars have similar but able to split it towards the rear instead

Viscous centre (i.s most manual 4wds) are the same as a viscous diff in that when worn out enough will just send more power to wherever it's easiest to send it, hence some cars barking up the fronts like mad on launch even though they're "fulltime 4wd"

It's like people arguing about "biturbo" vs "twin turbo" having different meanings

Edited August 18, 2015 by Marky

[lachlan]

this thread should have not got to this many replies .

[Sub Zero]

 lachlan said:

this thread should have not got to this many replies .

Haha I didn't think I'd get this many replies either to be honest.

[Koom]

I bought a random ty755* 5 speed that I think came from a Forester. It had a 1.1:1 gear in the transfer case so the front diff was a 4.444:1 and the rear was 4.111:1.

Which equates to sfa difference in torque split i.e. ~8% more torque in the rear.

[gotasuby]

The auto come with either vtd or clutch pack centre "diff " clutch pack range is 90:10 down to 50:50ax torque split. Vtd is 45:55 rear bias. Can lock up and increase torque either way depending on wheel slip.

Manuals with viscous centre are 50:50 until sustained wheel slip where the fluid thickens and transfers more torque front or rear depending on what axle is slipping. 4kg-cm is usual amount that can be transferred

Dccd diffs come in 2 different splits. Early is 35:65 and can lock axles together with clutch pack to allow anywhere from 100:0 - 0:100 depending on which axle has slip and mechanical grip of clutch plates. Later dccd 2005- are 41-59 and also have a viscous unit in them as well to prevent total unlock and drivers spinning out.

The 1.1:1 don't change torque split as final drive front and rear is still same.

Edited August 18, 2015 by gotasuby

[lachlan]

a dccd can not go from 100:0 to 0:100

its mechanical 35;65 and then can vary that to 50.50 via locking a clutch

[gotasuby]

 lachlan said:

a dccd can not go from 100:0 to 0:100

its mechanical 35;65 and then can vary that to 50.50 via locking a clutch

Wrong. If you take out the front drive shafts and lock the diff it will be rwd until you reach the torque limit of the clutch pack and it slips. Please get your facts right. That would be 0% torque front 100% rear. And vice vs

[Koom]

 gotasuby said:

The 1.1:1 don't change torque split as final drive front and rear is still same.

So you're saying that the front wheels spin 1.1 times for every 1 revolution of the rears........

If you run the same diff ratio front and rear with a 1.1:1 centre split, the clutch pack in the centre will give up pretty quickly cause it will be constantly slipping 8% when driving in a straight line.

[gotasuby]

 Koom said:

So you're saying that the front wheels spin 1.1 times for every 1 revolution of the rears........

If you run the same diff ratio front and rear with a 1.1:1 centre split, the clutch pack in the centre will give up pretty quickly cause it will be constantly slipping 8% when driving in a straight line.

No but for example the rear diff is 3.54 and front is 3.9. There is another 1.1:1 ratio drop hear in rear of gearbox on output. 1.1x3.54=3.9. Hence the output of centre diff for front and rear is the same speed.

[cods4]

 gotasuby said:

Wrong. If you take out the front drive shafts and lock the diff it will be rwd until you reach the torque limit of the clutch pack and it slips. Please get your facts right. That would be 0% torque front 100% rear. And vice vs

gotasuby is right. It took me a bit of reading to get my head round it, but a diff with a perfect 50/50 torque split is a totally open diff so the wheel with the least traction will spin faster, but both wheels will get the same amount of torque from the engine. When a diff is locked both wheels (or shafts) spin at the same rate. This means that the torque goes to the wheel with the most traction.

An LSD gives a healthy median between the two.