I have a 2010 STi hatch that I just swapped in a 2015 STI steering rack into and now I have a problem.
Going around moderately sweeping corners (~40 degrees) it feels like the car abruptly hits the brakes. Often accompanied by more of a grinding or binding type noise in the front. Oddly enough, the issue doesn't seem to occur if the car is being driven hard.
It was accompanied by a VDC traction slipping light and only occurred when off the throttle. After resetting/recalibrating the steering wheel angle sensor it occurs whether on throttle or off and there is no more slip light. Turning off traction control solves the problem.
When my mechanic plugged in a diagnostics computer and we did a quick run, the computer was showing that in those corners, some of the wheel speed sensors would read differently from others right when the issue was occurring.
One time it threw a code 071 for steering wheel angle sensor issues, after we cleared it, it didn't come back.
Really struggling here... it sure seems like the quicker rack ratio is screwing up the VDC, but it doesn't seem plausible that so many others have done this swap into a GR but randomly mine doesn't like it. The folks over at IWSTI seem to have that point of view as well.
TL;DR: Swapped in 2015 STi Steering Rack, now wheel speed sensors are reading oddly and the car drives strangely.