Help: Issue with ZF-6 clutch after dual disc install

[07keo02]

Well I just installed my South Bend dual disc clutch yesterday and I'm having a bit of an issue. Two things: The truck goes into gear okay, but it starts to engage literally as you release the pedal at all. Is this just because of all the space the two disc's and the center plate take up in the throw? Second thing, the pedal is having a catchy feel when I'm releasing the clutch after shifting gears. I don't think it is air but I guess it could be. My big fear is that a disc is catching on the input shaft of the transmission, giving me this catchy feel when it is slipping on the shaft. Hopefully, if this is the problem, it will wear together with time driving it. Anybody else have issues like this?

 

[04D_MAX]

try asking "dirty_max" think he had a simular problem, thought I read where some dual disc clutches are rediculous grabby

 

[messejme]

Air in the system can contribute to both of those issues. Remember that a dual friction clutch is made to engage harder than stock.

 

[SmokeShow]

There'll be virtually no slipping of the clutch. So as you begin to ease out off the clutch pedal it'll start grabbing immediately. At least in my experience it would. So it takes quite a bit more skill & precision with both feet to launch smoothly like normal w/o stalling it or taking off like a racer. Air in the system can contribute to that sensitivity though.

 

[07keo02]

I don't think I explained my self well in my Original post. I know they can be grabby, but that is not the issue at all. It starts engaging just off the floor, like I have to really press hard against the floor of the truck, pushing the pedal into the vinyl to get it disengaged all of the way. The pedal is also sticky feeling upon release, like it comes up half way, feels a little sticky, then pops up the rest of the way. I tried bleeding with the bleeder at the master reservoir but I don't think it was doing any good.

 

[07keo02]

I hooked the reservoir up to a bottle and bled all of the old fluid and air out. No change. I have heard horror stories of these thing getting air stuck in the slave but I don't know if that is my issue at this point. I 'm thinking I may pull the trans, check the input shaft and replace the slave and master cylinder together. Does anyone have the part number for the master cylinder?

 

[jc64]

Getting all the air out of the slave is a real pain. Ever since I put my single in (Valair), I have the same problem. The stock clutch would engage/disengage about mid travel of the pedal. Now it has to be most all the way to the firewall. I contribute it to not getting out all the air out. If I get lazy at a stop light, I can feel the clutch dragging. I have noticed that on warm days, the clutch is stiffer when disengaging it. For now I have found a band aid fix for it... I moved the seat up by a couple notches.

jc

Edit: I'm not blaming Valair, but the crappy self bleeding GM slave.

 

[07keo02]

And you replaced your slave right?

 

[messejme]

Sounds like air
Air compresses and you need a lot more travel tocompensate

 

[07keo02]

Not sure where to go from here with air. I disconnected the line that goes into the slave at the transmission and bled to there. I guess there may be a pocket of air in the slave that just won't come out. I'm going to drive it for a couple days and see what happens.

 

[dirty_max]

just drive it. I fought this problem for about a week after I put mine in. supposedly these things will bleed themselves out as long as you didn't get too much air in them. I had that problem when I very first started it up. I couldn't even get it to go into gear but I sat there and pumped the shit out of it for like half an hour and then I was able to get it into gear. over time it must have bleed itself out because pedal travel is back to normal. the only issue I have with the clutch now is that it is grabby as hell, but that's the way it was supposed to be. I have found that the harder I am on the clutch and the more I beat the piss out of it, the better it operates

 

[2006coalroller]

Mine was that nature of the beast try backing up a trailer little to say I have a alli now lol loved truck would kept it if i still lived in oregon but la traffic and that clutch no fun

 

[dirty_max]

Haha yea i was backin a trailer into a really tight spot a while ago and it felt like i had all 4 tires off the ground at one point

 

[07keo02]

Thats the weird thing, this thing isn't grabby at all yet. It's real smooth but starts engaging literally right off the floor. And the pedal is catchy upon release. I get a new slave tomorrow, I don't believe that this is normal symptoms, unfortunately. I will drop the trans Wednesday night if it does not improve, I think the slave may be the issue, but I'm not convinced something didn't happen to the input shaft and a disc is catching. Whats with the check valve just after the master cylinder on the line that runs down to the slave? Seems like I can hear an air sound a little bit when someone else is pumping but figured that might be normal while pumping.

 

[dirty_max]

ive always heard that sound. my clutch is grabby cuz it is the sintered iron disc rated for like 800 hp. i would not pull the trans back out too soon. i would give it at least a week. i replaced mine cuz my clutch came with one, but it wasnt anything special, just a factory gm one. if and when you do pull the trans put some graphite powder on the input shaft, it will help the discs slide better

 

[07keo02]

Did you also have the weird feeling in your pedal half way up after shifting a gear? The pedal feels perfectly normal sitting still and pushing it in and out. After I shift though and let the clutch out it feels like the pedal jerks slightly when coming up. This is why I was fearing a sticking disc. South bend literally told me to go out and beat on it a little bit and see what it does. I really want to trust you and their advice but I was supposed to take it 10 hours to Missouri this weekend. If I don't see improvement I might have to pull it and check it out.

 

[jc64]

And you replaced your slave right?

Yes, green GM self bleeding crap. I wish we had an option, but with only 7% (my personal guestimit) of the Duramaxes on the road having a manuals, your not going to get much aftermarket support.

just drive it. I fought this problem for about a week after I put mine in. supposedly these things will bleed themselves out as long as you didn't get too much air in them. I had that problem when I very first started it up. I couldn't even get it to go into gear but I sat there and pumped the shit out of it for like half an hour and then I was able to get it into gear. over time it must have bleed itself out because pedal travel is back to normal. the only issue I have with the clutch now is that it is grabby as hell, but that's the way it was supposed to be. I have found that the harder I am on the clutch and the more I beat the piss out of it, the better it operates

True that.

jc

 

[dirty_max]

i never really anything in the pedal itself, but yea when i get the pedal about halfway out is when the clutch really gets to jerking

 

[07keo02]

Well talked to south bend again today. He agrees it should come out at this point. If it doesn't clear up on the way home from the airport today its coming out tomorrow night.

 

[07keo02]

Hey guys need some quick advice. Got the trans down and see no fitment issues so I'm thinking the slave. The pressure plate has some heat mark ring around the inner surface already and was really warm by the time we got it down. Also the outside disk was turning darker on one side than the other disk, you guys think this is normal?