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Comment by ledriveby | Hacker News Reader

Subaru's higher end AWD system has separate output shafts from the engine for the front and the rear, with electronically-controlled clutches modifying the torque. Default is 60/40 front biased, but it can send 100% of the torque to either end of the car. Excellent performance with no manual mode switching needed, also manages good fuel economy at the same time. Best system in the business.

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Not quite. All AWD Subarus (i.e. except the BRZ) have one output shaft out of the engine, 3 out of the transmission/transaxle (2 to the front tires, 1 to the rear diff), and 2 out of the rear diff. Torque split varies between models and years with most near the 60/40 you quote, but the only one (in the US, anyway) that can send 100% torque to either end is the STI with DCCD on full lock.

However, if you don't have locking differentials you can still get into the situation where one wheel slips and the wheel that grips doesn't get any power - as shown by the Subaru getting stuck on the hill in this video: https://youtu.be/hrdb_UVTa20?t=543

There is a trick that seems idiotic but if you have a mechanical hand brake you can stop the wheel from free spinning. I'm not sure how well it would work for a front wheel, maybe you could hold the brake slightly while on the throttle. Again, seems ass backwards but if you think about what you're doing you're basically "locking" the open diff.

To add to confusion, Subaru sells several very different systems and calls all of them the same "all time all-wheel drive". There is viscous coupling center differential that goes with manual transmissions and nearly always splits torque 50/50 between front and rear, computer-controlled limited-slip clutch pack that comes with most automatics and changes torque split with speed, and some newer systems that do even more.

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