>> I think the new ones (WRX, anyway) are around 70/30 to 60/40.... the STi
>> is driver variable between 50/50 to 70/30... don't quote me on those >> numbers though.
>
> The WRX is still 50/50 with an LVCD. The STi is 65/35 Rear bias. The
> DCCD selects how open the differential is. It doesn't actually vary the
> torque split I can assure you (drive it on ice and you will KNOW it is not
> a 50/50 split). However, with the DCCD set to LOCK, the differential will
> lock up and does not need to detect wheel-spin before locking. With it
> set in AUTO, it will lock up the centre diff when it detects wheel-slip.
> However, it is pretty slow to do it on ice. I leave it in LOCK if the
> roads are really bad, or put it in LOCK to start, and switch it to AUTO to > cruise.
The WRX varies depending on the transmission type. The automatic has a computer-controlled "variable torque distribution" mechanism which can be turned into a pure FWD with a little fuse in the fusebox under the hood.
The front wheels of the 4-speed automatic have an open differential (unlike the STi) as do the manual transmission's wheels. Wide open. One front wheel can spin freely of the other.
The default split for the automatic is 45/55 rear bias. The default split for the manual is a straight 50/50, period. No variation.
The automatic transmission can vary it up to a maximum of 50/50 from its original 45/55.
For the STi, it's all different. The front wheels have a limited-slip differential apparently deliberately added to introduce understeer in an effort to "cup" the road better, according to a Japanese interview with a Subaru exec I saw.
The front differential type for the Subaru STi is a "Suretrac viscous limited slip", the center is a clutch-type limited slip, and the rear is a mechanical limited slip.
The centre differential can be driver-controlled: there isn't much detail about this mechanism in the user's manual for some reason, but in essence you can directly lock the front and rear wheels together for snowy or icy conditions in a 50/50 torque split (it works pretty well too,) or you can open up the differential as wide as a 65/35, which can allow a bit of wheel spin on the rear wheels during, for example, a hard launch.
I personally notice a definite improvement in forward acceleration when I fully open the DCCD, although the driving characteristics feel a bit strange by comparison with "Auto".
In locked mode, you can tell there's a difference when you drive very slowly in the tightest arc you can: the inside wheels will slip and shimmy. In auto or unlocked, there is none.