4x4 differential question

Silenceisbliss

hi guys,

have a question. I know full well how a differential works and that for 4x4's they generally have two. (as in one at the front and one at the rear axle)

my question is, do ALL 4x4 vehicals have 2 differentials?

we've a Kia Sportage and i find that when i have 4wd enabled, and i go from stand still to drive in 1st gear with the wheels turned a bit whilst on stones or gravel (not overdoing it at all with acceleration or anything), I find that the inside wheel spins and loses traction, as though theres no front diff. I can do it as slow as i like, same thing.

anyone care to comment?

colm_mcm

AFAIK the Sportage is primarally Front wheel drive and it has a 4WD on demand - i.e when the ABS sensors detect wheelspin it sends power to the rear wheels.

The torque is split front and back but it doesn't use limited slip diffs which means all the power will go to one side. It's not a 4WD system in the true sense of the term.

Even using the 4WD lock doesn't lock the diffs, it only distributes power 50:50 between the front and rear axles.
The system is good for countering wheelspin and torque steer but no good for offroading or slippery conditions.

Also note that the 4WD lock switches off once you go over 50kmph.

Silenceisbliss

cheers man!


that pretty much fully explains it. its an 05 model by the way, im sure that's no different regarding the drivetrain than the newer models.

colm_mcm

Nah, ironically the old Sportage (93-02) was way better off road as it shared mechanicals with Mazda 4X4s. the new one is much more on-road focussed.

WestWicklow1

I'm not familiar with the Kia Sportage but the fact that you can switch on 4wd means that it is a "Part Time 4WD" vehicle.

You should never drive a "Part Time 4WD" vehicle in four wheel drive on good traction surfaces because wind up will occur resulting in difficulty turning and possible transmission damage.

Permanent 4WD vehicles have a centre diff (that can be locked off road) to overcome this.

Have a read of our page here....

http://leinster4x4.ie/index.php?option=com_content&view=article&id=45:how-does-4x4-work&catid=36:transmission&Itemid=62

colm_mcm

There's a 4WD lock button on the dash but it isn't marketed as being a 4WD on/off switch. the 4WD is always lurking should you lose traction. having the 4WD lock switch activated means the rear axle is engaged, but as previously stated it's no good off road.

The Hyundai Tucson uses the same system (the new model Rav4 does too AFAIK)

Slidey

As far as I know it has an auto position on the switch to the RHS of the steering wheel.

There is also a manual position and a low position.

EDIT: I was thinking of the Sorento.

colm_mcm

you're actually better off with it turned off on slippery roads. not sure when it's actuallly of any real use. think it's just marketing shoite more than anything else.