FuzzyLog1c

iTrader: (4)

Background:

Just had my CTS-V tuned. Everything was running fine before the tune, and when I got the car back, it was nearly impossible to shift. The tuner thinks that it might be a bad LS7 pressure plate, but I'm not so sure. I still have the original LS2 slave in there with the Katech [edit: spacer, not pressure plate], so the clutch already engaged very low to the floor (translation: not much margin there).

Symptoms:

1. With the engine off, all gears shift easily.
2. With the engine on, but not moving, all gears are nearly impossible to shift into. The car moves forward slightly in first, even with the clutch all the way in, indicating that the friction disc isn't completely disengaging.
3. While driving, shifting is easy if I'm near the proper target RPM for the speed that I'm going, but hard if I'm not. I can hear the synchros working (sounds normal) when I try to shift.

Also note that I just bled the clutch with fresh Prestone DOT 4. The possibility of air bubbles has been eliminated.

Theories:

1. The slave cylinder is going bad and not giving me enough travel to fully disengage the friction disc (recall that with the LS7 clutch/flywheel/Katech spacer, it already engaged low to the ground).
2. The synchros are going bad for reasons unknown.
3. The LS7 pressure plate is defective (has less than 50 miles on it)--perhaps a couple of the fingers are bad (but they looked good when I installed it).

Ideas?

raven154

iTrader: (14)

Honestly, I would keep bleeding. The symptoms you posted point to air in the system. Usually when a pressure plate goes bad they start to stick to the floor under hard acceleration. When a slave goes bad, they generally pop and you lose everything. Air can be tricky to get out because the shape of the GM slaves don't make it the easiest to get all the air out. Trust me, you can bleed and bleed and think you are done and then all of this sudden, more air starts coming out. F-bodies have the same problem.

I can assure you that I am not the only one who will recommend this. Just for giggles you should post this same question in the manual trans section and see what they say too.

meatyCTS-V

Bleed it.

-meaty

STAGEUP

bleed it, if that doesn't work, check the torque on the pressure plate bolts, they may be over torqued

NeverSatisfied02

iTrader: (12)

I've had my clutch pedal stick to the floor a couple times but always comes back up if I lift it or pump it. Not really sure why it happened but it seems to only happen after spirited driving and it happened again when I was cuttin a few donuts in a parking lot. Lol Wonder what the issue is? I'm on a stock clutch in mine.

raven154

iTrader: (14)

Could be old fluid. Just a good flush can fix a minor sticky pedal. When flushing and bleeding stop working, replace the pressure plate. At least that has been the case for me and many others on here I have seen.

FuzzyLog1c

iTrader: (4)

Let me grab a friend and run through another bottle of DOT 4. I'll report back when finished.

punishmentcycle

iTrader: (6)

Get the ls7 slave.. it will solve your low pedal problem.. as far as it trying to move in first with the clutch in... it sounds like the pressure plate wasn't installed right.. if u don't tighten and torque in a star pattern the clutch will stick in certain spots.. I've seen it happen a few times

FuzzyLog1c

iTrader: (4)

I know you're not trying to be demeaning, but everyone on this forum should know the star pattern by heart.

In short, that's not the problem here--I torqued the flywheel and pressure plate bolts to spec in the usual star pattern (new GM bolts on the flywheel, btw).

Besides, there was no problem with shifting before the tune. Post-tune, it's almost impossible to get into reverse, and the forward gears are difficult to shift into when stopped. Once moving, everything's pretty much normal. Still waiting for a friend to depress the clutch pedal so that I can bleed the clutch a little more. As before, I'll report back when I'm done. In the meantime, I'm taking this opportunity to bleed the brake lines and power steering fluid.

punishmentcycle

iTrader: (6)

By no means was I being demeaning.. I don't know u r what u know or don't..just trying to help.
a tune wont affect shifting on a m6 .. only thing I can think of is something happened on the dyno ghat might have fried the clutch. Did u break the clutch in before the dyno?

raven154

iTrader: (14)

Personally I have had the best luck bleeding it by myself. It's a pain in the *** but what I did was pump the pedel and leave it up. Get under the car an open the bleeder. Now push the pedal down slowly. Close bleeder and pull pedal up very slowly. Now pump pedal until you get a good pedal again and repeat. That is the best way I have found to do it. I had a pretty bad run of luck with failing slaves and have had more than my fair share bleeding this damn thing. Worst part is I don't have anybody to help me! Trans out and in and clutch bled all by yours truly.

FuzzyLog1c

iTrader: (4)

Raven, you da man! First to respond, had the right answer, then doubled down and gave me an idea for a one-man bleeding technique. If you ever show up in CT, I owe you a beer.

In short: the clutch is back to normal. As suspected, there was still some air in the system. Since I already got most of the air out of the system (had some feel in the pedal), I normally would've relied on a helper to finish up the bleeding process. Based on what Raven said, however, I tried unscrewing the remote bleeder valve to the point where I'd get a drop of fluid every 1-2 seconds (meaning that there was only a very narrow opening), then forcing the clutch pedal to the floor.

Normally, with a fully-open valve, you'd introduce some air back into the system because everything in the slave / remote bleeder line would run right out. With the valve barely cracked open, however, once the pedal went to the floor, I was able to get under the car and close the valve before all of the clutch fluid had drained out of the line.

STAGEUP

Gravity bleeding works great too.