Originally Posted by Tommy Boy
Well it certainly can cause a 4 wheel drift on dirt which you don't really want. You want the rear end to drift and the front wheels to have traction for steering. Thats why most of them have viscous center diffs so you can adjust the power ratio front to rear. You can split the power like 30/70 front/rear so you don't get the loss of traction and understeer that comes with the front wheels having too much power.
Yep. A lot of older AWD cars will have inherent understeer because the power is generally split about 50/50 give or take, but nowadays a lot of AWD cars like the WRX STI and the Lancer Evolution use an onboard computer to determine when you need more power in the back etc etc. It's the same with Nissan's ATTESA system and BMW's xDrive. If the computer detects loss of traction as you're cornering, it'll send power to counteract the loss. That's why you can have such heavy cars like the GT-R and X6 handle so well despite the fact they weigh upwards towards 4000lbs.
Audi still uses their Quattro system today, the same system the revolutionized rallying when the first Audi Quattro debuted. For their newer cars they usually split the power about 40/60 (front/rear) so you can still apply throttle like it's RWD and not lose traction at the same time.
As for rallying, they do drifts cause it's just the fastest way around sweepers and hairpins. Grip racing is still naturally faster than just drifting, but in dirt that's the opposite because usually you have nothing to grip to start with.