I have autocrossed in an auto GXP and it was very fun.
The first thing to do is get an aggressive alignment. After that, put the gear selector in L and have fun. We found that the auto will shift to 2 at redline and then back to 1 while braking in this position.
The biggest problem the auto has versus the manual is getting the front end to grip when off the gas. In a manual you can let off the gas, the engine will wind down a bit, transfer some weight to the nose and the front tires will grip. In the auto letting off the gas only engages the torque converter meaning the nose stays light and the front tires won't grip as well as they should. Left foot braking makes a big difference and helps to make the car faster on course but the manual looks to be the better autox choice.
My buddy (who has spent some time and $$) developing his auto GXP for autox is currently looking into how to get a manual trans car. The auto has served him well and was fun enough to thoroughly addict him to autox

but ultimately the manual will be better.
If you think that you'll only autox occasionally then get out there and hit some cones and have fun. The auto GXP is still a very satisfying drive at the autox.
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Red Bull Drift Team 2008
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