Streetk14

Did some searching and found 1 old thread that fits my issue to a T: http://forums.corvetteforum.com/c6-c...sing-feel.html

It really doesn't seem to hurt anything, but bugs me and doesn't seem normal. Basically, on a full throttle pull through 3rd or 4th gears the pedal will sink down an inch or two. It does this without any shifting or clutch use. High power or RPM seems to cause it. It returns to normal within seconds of backing off the throttle.

Anybody else have this problem with the LS9 clutch? I actually have the Katech LS9R version (good to over 900 flywheel torque) in my supercharged LS3 car. Car makes around 665 rwhp and 570 rwtq, for what it's worth. No slip is being noticed and the torque capacity should be more than enough for me. I haven't done any hard launches on it, either.

I'm hoping it's just a fluid/bleeding issue. The good news is that I have a Katech remote bleeder, so I will do a real bleed on it when I get time. Hoping that will fix it. The other thing I don't like is how close the stock LS9 clutch line is to my header tube. The line is covered in some sort of heat wrap, but maybe the fluid is getting too hot during hard pulls? Just thinking out loud...

I'd like to hear if any similar issues you guys have had and any cures -- or if this is a normal LS9 clutch function that I just live with. Thanks

timvette7

Mine is completely stock and had the same problem a couple times and found out that is was the clutch fluid. It was totally black with only 1700 miles on it. Changed it and it hasn't had the problem since. Check on YouTube rangers method to changing the fluid.

Tim

Streetk14

Thanks. I always did the "Ranger" method with my original LS7 clutch and never had any issues. My fluid is very clean and the clutch/slave/bleeder only have around 1000 miles on them. However, if your stock car was fixed with a fluid change, maybe I have some debris or air in the system as it was just opened and new parts installed.

I'm actually really glad I did the Katech remote bleeder now. Really should be a better solution than the "Ranger" method.

BTW, did you have the dealer bleed yours under warranty?

timvette7

Yes the dealer did do it under warranty.

titletaker

My buddy with a 2010 has the same concerns and it drives him crazy, but doesn't seem to have a direct effect on the cars performance. Mine doesn't do this, but I have had my slave cylinder replaced under warranty for failing.

Streetk14

Good stuff.... So they most likely got to the bleeder on the slave and actually did a true bleed on the system. I will do the same and let you know how it goes. Thanks

Streetk14

Yeah, doesn't seem to hurt anything -- but it does bother me. A brand new ZR1 slave went in with the clutch, but it doesn't mean some air isn't still in the system somewhere. We shall see...

Fartpipe

Well if you remove the stupid clutch return spring that pulls the pedal down to make it easier to push it helps with that greatly. My car if I rolled into the gas in 3rd gear down the highway would sink to the floor almost and my clutch fluid would turn pitch black in 3 miles. So I tried removing the spring and yes the pedal is a fair amount stiffer but the fade doesnt happen no where near as much and my fluid doesnt get dark any where near as quick. This by no means increases performance but does help for clutch longevity IMO.

Note:I've had another member see if their pedal faded and it didnt fade any where near as much as mine. His fluid doesnt get dark easily either. I'm guessing some springs are stiffer than others causing the fade to be more prominent.

range96

This is strange. You're saying the pedal sinks as you accelerate without touching it?

Streetk14

Yep, pretty much. I usually notice it when doing hard pulls through 3rd gear. When I go to shift into 4th, I feel it in the pedal. It will either drop an inch or so, or I just notice more free-play in the pedal before the hydraulics seem to do anything.

I've now chatted with a few other ZR1 owners with the exact same issue. They were all cured/improved by either a proper clutch bleed or just keeping the fluid extremely clean.

Like I said before, it really doesn't seem to cause any release problems. I just ran the car hard at Shift-Sector's 1/2 mile airstrip event and all was well. Actually, I did miss 3rd one time -- but that was probably me, not the car.

BgBoost1

I have ran into the same situation using the same clutch. My Fluid is clean and is kept clean and it is still happening. It is annoying and causing me to miss gears from time to time. NEVER had that issue with my stock clutch.

I just bought a Tick Master and will see if that cures the problem. I will let you know if it does.

Joezone914

Mine has done it a few times. Strangely I did not notice at the DE i did. Just on the street a few times.

Streetk14

I did a quick bleed on the hydraulic system with my remote bleeder the other day, but I haven't had a chance to take it out and drive it hard. We will see if it helps with the pedal problem

On a side note -- with the bleeder open, you really get a feel for what that pedal spring is doing. It basically sucks the pedal to the floor when pushing the pedal down. Makes me think it's there in part to slow down the engagement of the clutch like a delay-valve on some cars.

Streetk14

Ever get that Tick master installed?