SpartanSD

Hi guys, '14 C2 w PDK here. When the hill holder releases, most of the time it does so with a violent shudder that cannot be right - especially since the same feature on my wife's Volvo is completely imperceptible. There have been several threads in the past about potentially coding out the feature, but I would prefer to actually fix the problem. Has anyone encountered this, and more importantly has there been a fix? The system seems simple enough, and I'm guessing it's a stick/slip condition on the parking brake shoes. I could try replacing the shoes, but I'd like hear of anyone's experience before I go to the work. The only other thing I can think to play with is the shoe clearance adjustment, but the diagnostics say it's in spec. Any wisdom out there?

subaru335i

It could also be the engagement point of the PDK clutches. You could try to get a relearn done on the PDK.

Do you have any rough shifts any other times?

SpartanSD

That's a thought, but the PDK is well-behaved - certainly doesn't make any fuss when pulling away from a stop when the hill holder was not activated. Of course, I'm assuming here that the hold feature is executed by applying the parking brakes - I could be wrong about that!

asellus

The hold feature is done by maintaining the brake system pressure once applied, I believe through the ABS system? Some kind of selectively one-way valve in there, not sure on the specifics. After a minute or two, the hold feature will swap over to using the parking brake instead, lighting up the red brake light instead of the green hold light.

The parking brake is electric and rear wheels only -- you can clearly hear its actuation when it happens!

Any violence would be caused by poor PDK clutch calibration or the brakes not releasing as quickly as the car expects them to.

SpartanSD

Thanks, that's helpful.

Bud Taylor

Either. It grabs too hard on disengagement. I think its a software thing. I have a MT.

vanlieremead

And I’m sure you have renewed your brake fluid recently enough. But you might want to inspect those rear brakes for evidence of distress, broken springs, etc.