Spent the past few hours reading through all the related threads, but they all seem to be full of guess work (drill mod, air in system, bad pressure plate, shims, adjustments, etc). Trying my luck posting about my symptoms.

Details:
2001 Pontiac Trans Am WS6, 144k mi.
Previously replaced the Master Cylinder that went out a few years back, never had any issues.
Factory clutch was not slipping, no issues other than a rattle when clutch pedal is depressed. Figured it was the slave cylinder so I bought one from LuK. Had a buddy who has a C6 Vette who swapped his factory clutch out with an aftermarket since he knew it wouldn't hold when he added a blower, so he gave me his LS7 Flywheel, Clutch and Pressure Plate (only had ~30k mi on them). Figured I'd throw those in since I had to remove the transmission to replace the slave.

Removed the trans, sure enough the release bearing is shot and causing the rattle. Replaced it with the new one from LuK. Factory Flywheel/PP/Clutch still looked great (keeping it as a backup), noticed it had LS6 part numbers (not sure if that's normal). Pilot bearing was shot, so I replaced it. Didn't do any adjustments on the LS7 Pressure Plate. All the LS7 components bolted right in without issue. No trans fluid leaks. Everything looked great. Bolted it all together, bled it a few times, pedal felt stock, fired up, shifted okay (slight extra effort), drove great.

Parts:
- New Master, replaced approx 2yrs ago (No drill mod)
- New Slave
- New Pilot
- Used (30k) LS7 Clutch, Flywheel, Pressure Plate
- No Shims
- No Adjustment

Symptoms:
That was Sunday. It's Tuesday, approx 150mi later. Very difficult to get into reverse. Lots of effort to get into gear while driving or idling. Shifts into each gear like butter (except reverse) with vehicle off. While idling, if I shift into 1st without letting off the pedal, it rolls forward (on level ground).

I'm ruling out forks/linkages since it wasn't an issue previously and because it shifts fine with the vehicle off. Reverse could be due to a lockout, but I see where the previous owner (I bought it at 44kmi) has spliced into the wire at the PCM and may have done the lockout so I'm not sure why removing and installing the trans would interfere with that unless I knocked a wire loose. It's possible there may still be air in the system so I plan to bleed it again, but I'd figure I'd pick everyone's brain for other things to check when I get around to doing it. I've read mixed feelings about adjusting versus not adjusting the pressure plate. I've read mixed feelings about shims. I'm down to two possibilities: air in the system and/or pedal travel adjustment.

 

Update:

Using a MityVac, I reverse bled it through the reservoir. I pulled out a lot of air, but I honestly can't say that resolved my concern. It's still difficult to shift and feels as if it just barely disengages with the pedal applied because I can release the pedal just a hair and the vehicle starts to shake, letting me know the clutch is engaging.

It doesn't seem to roll forward anymore with the clutch disengaged and in 1st gear, but it doesn't seem to have resolved the shifting difficulty. At this point I'm down to the possibility of air in the system due to a leaking Master/Slave, or pedal travel adjustment via an adjustable master cylinder.

The Master was never touched and wasn't leaking prior to the repairs, and the Slave is new. Unless the slave is bad, the bleeder is leaking, or there's a hydraulic line connection/fitment issue, then I'm not sure what it is unless other parts just decided to take a **** at the same time--and trust me, my luck IS that bad. From what I've read, there's no factory adjustment to clutch pedal travel without using an adjustable master cylinder.

I'd hate to needlessly throw parts at it, but I'm running out of ideas.

 

It would be nice to be able to be under your car to see just how much the throw out bearing is depressing the pressure plate. My guess is at this point that it's not pushing it in enough and you may need to shim.

 

Wouldn't the same thing be accomplished with a larger bore/adjustable master cylinder? I'm curious as to WHY I might need a shim and/or adjustable MC. What's causing this issue? I had the assembly I took out next to the LS7 assembly, and while I didn't actually measure it, they looked almost identical in height. Is there a difference between the height of the two assemblies that may be causing the Slave not to fully engage the diaphragm spring? I've seen mixed threads about having to adjust versus not doing a thing other than bolting it on when it comes to the LS7 assembly swap. I feel like if there were a definite height difference, there would be a unanimous "you're going to need to buy/do XYZ".

 

Wouldn't the same thing be accomplished with a larger bore/adjustable master cylinder? I'm running an adjustable which allows me to adjust the clutch pedal but I'm not sure it adjust the travel of the throw out bearing since the slave is hydraulic.

 

Perhaps the diaphragm spring between the LS7 assembly and assembly that I took out are of different heights, with the LS7 being a bit more shallow. If that's the case, the SC would have to travel farther to engage it fully. Right now it feels as if the clutch would fully disengage if I had another inch or so of travel, but instead I'm hitting the floor. If I were able to adjust the pedal height as well as push more fluid, wouldn't that cause the SC to engage the diaphragm spring sooner, thus pushing it further? It's also likely that my current MC decided to start taking a st!t on me, which may also be contributing to these issue by allowing a bit of fluid bypass/leak-back.

 

As of lunch today, it'll no longer go in gear with the car running. I can shut it off and put it in 1st and start the car, but I have to hold the brake. Naturally I hit every stop light as well. I ordered the Tick Master Cylinder and am waiting for it to get here, but that won't fix it because, as difficult as it is to install, that's too easy. The problem will probably end up being my new Slave cylinder for the simple fact that I just ordered a Master, and because I have to drop the trans to change it.

 

Ls7 clutch is poop.

 

Update:

Installed Tick Master Cylinder, bled 1000 times via MityVac. Got to the point where, while idling, 1st-4th felt pretty good. Slight bit of resistance, but definitely not what it was (having to force it in). Not smooth like before I ever touched it, but still better than not going in. Reverse was okay. 5th was difficult, 6th a little less difficult than 5th. Not sure if any of that much mattered since I was idling. Took it for a test drive and it drove okay. A little resistance in all gears but definitely not bad. Only drove it a couple of minutes (around the neighborhood behind the shop). By the time I got back, it was done. Wouldn't shift into any gear at idle, and would grind when trying.

 

Did it loose any fluid?

 

No fluid loss.

 

Your sure there is no air trapped in the slave cylinder? Also is this a new slave cylinder or an old one that may be worn out.

 

It's a new slave cylinder. There may be air trapped in it, sure, but after bleeding it as many times as I did, I'm starting to feel like that's just everyone's go-to guess. I literally bled it for about an hour and a half last night. Why would air in the system cause it to revert to not shifting after driving it for 2 minutes, especially when it was shifting fine(ish) prior to driving it after I bled it? Heat?

If it's leaking past the slave internally, wouldn't putting in a new master do absolutely nothing? Meaning no amount of bleeding would be changed it from requiring excessive force to shift? Or is it still leaking internally and the fact that I put in a Tick Master that pushes more fluid temporarily allowed the slave to perform as it should?

Did I over-extend the Tick Master's rod? I followed the instructions and started at the lowest setting. I'm probably 8-12 threads from that, now. If I over extended, what are the symptoms of bending the diaphragm's fingers?

 

As long as it is lower than the brake pedal your probably okay there. To bleed the slave usually takes two unless you have a remote bleeder on the slave but the process goes like this

1.) Open bleed screw
2.) Press in clutch and hold
3.) Close bleed screw
4.) Let off the clutch pedal

Do this several times to make sure you have all the air out of the system and top off the fluid reservoir. Just make sure to keep plenty of brake fluid in the reservoir so you don't end up drawing in more air into the system.

 

I've done it by myself I just had to have something long enough to push and hold in the clutch.

 

 

Didn't know man I'm just trying to help. Once you find out what the root cause is be sure and let us know.

 

No worries man, it's just driving me insane haha. I'll definitely update it as it progresses so maybe it'll help others sometime down the road (pun intended).

 

They can be a pita sometimes. Best advice i can give is to trash the stock hydraulic release bearing. Go with a tilton 6000 .

 

I don't have another $600 to drop for their slave cylinder. It may be good, but I can't justify $600. The stock one lasted ~144k before the release bearing went out, the slave was great. LuK makes GM's slaves and clutch assemblies, and that's what I have in it, so this is basically OEM. And for less than $100, this slave (should) last me another 150k.

I cracked the bleeder on the slave and attached a pressure bleeder to the reservoir. As soon as I applied pressure, it started shooting out the slave, so there's no air in the system. Tested it again, no change. Still grinds in reverse.

At this point I'm guessing the new Slave that's in it is leaking internally, but I have no way to test that.