Ipecac

At a recent HPDE day at Laguna Seca I started experiencing two new problems with the car and after doing some research I still can't figure out what the problem is.

Car: 2011 z06, in competition mode.

#1. When tracking out of turn 11 (slow 90 degree left, onto front straight) I would start to get on the gas and there would be a clunk on the passenger side followed by the car struggling to put power down. Almost like it would buck on and off the power, like some sort of assist was kicking in. It would do this intermittently at other sharp left hand turns, but it always did it at 11.

My first guess was the wheel bearing/hub. But I did have the left front drivers hub fail on be before, and this feels nothing like that. The other thing I thought it could be was a broken end link, but I suspected I would feel that more frequently.

#2. The second problem, which may or may not be related, was a lock out of 2nd and 3rd gear. It felt exactly like the skip shift was activated, but I was beyond the limits that would kick in at and the light on the dash did not activate. This continued to be a problem even on the drive home. I feel like this happened once or twice when I first got the car, but it hasn't been an issue for over a year.

I'm wondering if the solenoid that controls the skip shift could be broken. Or come to think of it, this did happen right around when my other hub failed. Could these be related?

Also, I took the car on a long casual drive yesterday and didn't have a single problem.

Anyhow, I appreciate any input as I try to get the car in working order for the next HPDE.

ErnieN85

#1 check for codes it is probably the wheel speed sensor in the hub, caused by bad sensor or a loose hub.
#2 get a skip shift eliminator it plugs into the harness in place of the solenoid. that will make sure the 2-3 problem isn't that
Go from there

Bill Dearborn

I will take a different angle than Ernie did. When active handling engages sometimes it can feel and sound like something hit the car. You were running a 90 degree slow left hand turn and maybe the back end started swinging to the right. Active handling would apply the right front brake to slow the yaw to the right and bring the car into line. Sometimes you feel an ABS like vibration when it does that but I have experienced large hammer like impacts where the brake is applied so hard that it makes that side of the car feel like it dragging the tire.

Did you feel any hint of the backend being loose and maybe starting to come around?

As for the shifting issue did you notice whether or not the clutch was starting to drop lower and lower?

Bill

Ipecac

Thanks for the responses guys. Bill, you may be on to something.

When my previous hub failed it was causing problems during higher speed corners. It would force the wheel to kick back to center. It was always random and I had trouble recreating the issue on demand.

This feels more like the brakes are being applied to the outside wheels or the power was being cut. It would sort of pulse 2-3 times before I would have full power. It would come on during track out when applying the power. I would say its right before the rear would have kicked out, but I put on new R888s and they just have grip for days.

Perhaps I just need to get back out there and run with all controls off. That said, I am also going to pick up a diag device, just because it would be a good to have.

Re: the transmission. Everything else felt perfectly normal. I want to get under the car to see if the previous owner installed a skipshift bypass that is malfunctioning, because it feels exactly the same as when it is active and it only does it for those gears.