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Clutch Question

Old 04-18-2018, 08:40 PM
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Withnasty
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09 Z51 M6 25k miles headers back, intake, and tsp stage 3 cam. Ive been having clutch issues for a while, slips in 3rd or higher above 4k rpm and/or when shifting hard. bled the clutch a few times as the fluid gets filthy really quickly and itll grab for a while after a fluid change. ive pretty much settled on just replacing with a monster lt1s with the billet support bearing and a new slave. my question is, and this might be indicative of further issues, but i've tried to practice launching a few times and with the clutch pedal in when i rev the car it pulls the pedal down and it wont release/engage. Im assuming as the car builds vacuum its doing something to the master cylinder?
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Old 04-18-2018, 08:44 PM
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phils C5 vette
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your making more HP than the stock clutch can handle.

Last edited by phils C5 vette; 04-18-2018 at 08:44 PM.
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Old 04-18-2018, 09:57 PM
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Withnasty
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Originally Posted by phils C5 vette View Post
your making more HP than the stock clutch can handle.
it only makes slightly more than a stock z06. i was under the impression the clutch was the same as a z.
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Old 04-19-2018, 07:13 PM
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Originally Posted by Withnasty View Post
it only makes slightly more than a stock z06. i was under the impression the clutch was the same as a z.
How much did your car make at the rear wheels? Over 505 at the rear wheels maybe?

There's a big difference in what you make in rear wheel horsepower vs. crank horsepower.
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Old 04-19-2018, 09:08 PM
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Originally Posted by jaybee924 View Post
How much did your car make at the rear wheels? Over 505 at the rear wheels maybe?

There's a big difference in what you make in rear wheel horsepower vs. crank horsepower.
It made 480 to the wheels so even on the conservative side, thats only 550ish to the fywheel
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Old 04-20-2018, 02:06 AM
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Originally Posted by Withnasty View Post
It made 480 to the wheels so even on the conservative side, thats only 550ish to the fywheel
You may have a one of the older master cylinders that were prone to have engagement/disengagement issues. I think GM put a revised one out that around in the 2011/2012 C6 from what I've read over time. It has DOT4 on top of the cap. I could be wrong on that. Look up clutch stuck to the floor or Master cylinder and that may can help you out.

You also have to remember that yes that's a little bit more power than the Z06 but your are starting to beat on it which will shorten the life of it but if you an get a different master cylinder GM/maybe Tick it may help or the damage may already be done.
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Old 04-20-2018, 10:47 AM
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Mike's LS3
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The LS3/7 share the same clutch and with 480 rwhp it has more room to grow.

I would take the least expensive approach and replace the clutch master cylinder and add a clutch bleeder. Flush with D0T 4 and see if there is any improvement. The new clutch master cylinder design has improved seals and a black reservoir vs. white on the old one. I had the clutch master cylinder covered under service bulletin warranty, you still might be under warranty.

If that doesn't work, then replace the clutch.

25k on a clutch is low mileage, unless it was abused.

Last edited by Mike's LS3; 04-20-2018 at 10:52 AM.
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Old 04-20-2018, 07:50 PM
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Originally Posted by Withnasty View Post
09 Z51 M6 25k miles headers back, intake, and tsp stage 3 cam. Ive been having clutch issues for a while, slips in 3rd or higher above 4k rpm and/or when shifting hard. bled the clutch a few times as the fluid gets filthy really quickly and itll grab for a while after a fluid change. ive pretty much settled on just replacing with a monster lt1s with the billet support bearing and a new slave. my question is, and this might be indicative of further issues, but i've tried to practice launching a few times and with the clutch pedal in when i rev the car it pulls the pedal down and it wont release/engage. Im assuming as the car builds vacuum its doing something to the master cylinder?
If the fluid is getting nasty really quickly, you have a LOT of accumulated clutch dust on the slave side. I had to do the reservoir flush every weekend for almost 3 months before it started getting clean. You may want to try that before doing anything major.
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