I got this directly from Bill Boudreau (www.zfdoc.com). As most of you know I have been fighting Clutch Hydraulic Issues for the last month. I went through 5 Masters and 3 slave Cylinders, The Last set being the Aftermarket Cast Units. Now the findings posted regard to the DOM (Drawn Over Mandrel) Cylinders only, Neither Bill or I have disassembled a Cast Slave yet, so we are unsure if they are an issue at this point. If my Hydraulic don’t work for very long with my cast pieces I will take the cast one apart.
So here we go:
It appears that the Seal on the piston in the slave cylinder is installed backwards. One picture below shows the correct and incorrect direction for the Seal. The second picture is a cutaway of the Slave. Bill found this on 2 BRAND NEW Slaves (from GM I believe)
I disassembled 3 Slaves I have. One purchased from The Last Detail in September of 2004, it was in a GM box. One was from Corvette America Purchased in September of 2005. The last one was purchased in May of 2006 from CARQUEST. When I disassembled the Slaves I found ALL 3 to be wrong, the seal was backwards. The GM one I had (From Sept. 2004) also had an external leak which is why I initially changed it, but kept it around for the bleeder and push rod. I contacted Bill with my finding and he will contact a person with GM. So basically this problem goes back to at least September of 2004, maybe before then.
The pictures are from Bill B. I want to thank him for helping me and letting me know what he found. He and I agreed that with my specific problem and the Slave will act as if it was good but is the seal swells it could get stuck in the bore ½ way. I even saw this on the CARQUEST slave that I got. With the Seals corrected that seem to work much better, I know neither leak so I have 2 good parts as spares, assuming the Cast unit works fine.
Location: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
The one pictured is assembled incorrectly? Looks like some idiot forgot which side the fluid goes on.
I'm going to pull mine apart this weekend and check it I guess. I'd think this was almost funny if I wasn't bit by it too. So let's find the guy responsible, and give him some Chinese brake-fluid torture. Maybe a good soak will make the rest of us feel better who've been soaking ourselves in brake fluid replacing these.
Last edited by CentralCoaster; 05-25-2006 at 10:56 PM.
The one pictured is assembled incorrectly? Looks like some idiot forgot which side the fluid goes on.
I'm going to pull mine apart this weekend and check it I guess. I'd think this was almost funny if I wasn't bit by it too. So let's find the guy responsible, and give him some Chinese brake-fluid torture. Maybe a good soak will make the rest of us feel better who've been soaking ourselves in brake fluid replacing these.
I zzomed in on the picture I got from BIll of the assembled cutaway, it is correct just hard to see.. As I zoomed it got Pixelated
Thanks =jeff= Mine is also installed backwards. Seal looks pretty good will check close tomorrow and put back together. Hadn't really checked seal close because of problems with bore surface. I don't feel too dumb about missing it because DRM missed it too! toetap:
I'm gonna check my new in the box one I just bought, besides checking the one I just re-built & have in the car now! It would be nice if this was/is my problem...because I was starting to think about things that would require trans r & r!!
Thanks again to you guys!
Oh, this may help the guys with bore problems: If you have a brake honer warp the stones in 600 grit wet paper, use DOT3 as a wetting agent, and hone the bore that way. If you can get the scuff marks 90% gone the slave maybe okay. I used that method on my bores using my Ryobi on high, I guess a vari-speed drill would be okay also. You don't want to go too far but if the 600 paper cleans it up you might have a spare that's good.
I'm gonna check my new in the box one I just bought, besides checking the one I just re-built & have in the car now! It would be nice if this was/is my problem...because I was starting to think about things that would require trans r & r!!
Thanks again to you guys!
Oh, this may help the guys with bore problems: If you have a brake honer warp the stones in 600 grit wet paper, use DOT3 as a wetting agent, and hone the bore that way. If you can get the scuff marks 90% gone the slave maybe okay. I used that method on my bores using my Ryobi on high, I guess a vari-speed drill would be okay also. You don't want to go too far but if the 600 paper cleans it up you might have a spare that's good.
My 3 slaves bores looked good, although one of them had an external leak and was junk anyway..
Any one have the P/N and mfg & whom did you get it from for the cast slave cylinder? Thanks
I just aired up my new slave and the piston seal was on backwards. It was a Raybestos/OEM type, the steel type that looks exactly like the OEM stuff you get from the chevy parts dept. I just got the slave last week from RockAuto.com(not their fault)
I'm using the wagner cast type M/C so I figure I should buy a cast slave to go with it. This has to be the longest I've worked a problem & didn't get to a solution...
Location: SCMR Rat Pack'r Charter Member..Great Bend KS
I can imagine it went down like this:
( Scene at hydraulic components assembly line: )
"Hey! Francine! I just discovered that these little doo-hickies go into the bigger doo-hickies a ho' bunch easier if you install that little black rubber thingie on the little doo-hickey backward!!"
"Well, by golly, Edna Mae, you is right! And who is going to know the difference anyway.... he, he, he. We is just too durn smart!"
I have a new, uninstalled sc that I bought from CC last year. I will be installing it this summer.
If it's easy enough to disassemble and check the seal, I'd be inclinded to do so. Can anyone confirm if Corvette Central's are likely to be flawed and/or how hard it is to r/r the internal piston to check the seal installation? Special tools?
I can only say that the first slave cyl I bought was from a chevy dealer last summer. Proly about July. I put it in and in a little while I started having trouble with noise coming from the trans when I stepped on the clutch. That's when I started down this road. Maybe you should check it before using it.
You need a decent snap ring tool. Compressed air to blow the piston out. 13mm for the bleeder and 14mm for the line connection and 13mm swivel socket + a bunch of extensions for the slave r&r. Mind that you clean out the cylinder as I've found metal in all of my new ones. It isn't hard to do with compressed air.
Any one have the P/N and mfg & whom did you get it from for the cast slave cylinder? Thanks
I just aired up my new slave and the piston seal was on backwards. It was a Raybestos/OEM type, the steel type that looks exactly like the OEM stuff you get from the chevy parts dept. I just got the slave last week from RockAuto.com(not their fault)
I'm using the wagner cast type M/C so I figure I should buy a cast slave to go with it. This has to be the longest I've worked a problem & didn't get to a solution...
Tom
Cast slave is from partsamerica.com
TRQCS360017 CLUTCH SLAVE CYLINDER $76.88
As for Wednesday evening they were out of stock.. in fact the one I got was used and returned and sent to me.. it had a bent push rod. I used a spare push rod, if it works, I will get some $$ back from them for selling me a used part.
...to Jeff and every one else that helped track down this issue!!!
Thanks again for the source & P/N's Jeff!
This always reminds me that with this hobby it's not just about the cars...it's the people you meet while you're in the hobby that makes the cars more enjoyable! Thanks guys!
uh oh.. Are they ALL bad?? I just opted to replace my perfectly good non leaking slave with one from GM since the entire drivetrain was new front to back. My pedal does squeak when pressing the clutch in.. could it be because of the mcleod unit? Is it hard to remove the slave ? I may just put the original back on and send the new one i got to get fixed.
uh oh.. Are they ALL bad?? I just opted to replace my perfectly good non leaking slave with one from GM since the entire drivetrain was new front to back. My pedal does squeak when pressing the clutch in.. could it be because of the mcleod unit? Is it hard to remove the slave ? I may just put the original back on and send the new one i got to get fixed.
The squeak usually is caused by using DOT3 fluid in place of GM Hydraulic Clutch Fluid. The DOT3 doesn't have some of the friction modifiers that the Hyd fluid has. I ran up against that when a dealer did my M/C & found that answer at zfdoc.com.
It seems to be the case with the slave piston seals. I just got one last week and took it apart & found the seal on backwards. It was a Raybestos boxed slave...they look exactly like the slave you get at a chevy parts counter so I guess Raybestos makes them for GM??
I have come to not trust any of this stuff any longer based on what has been found out by guys like Jeff. I'm installing the "new" slave I got last week...but I took it apart and corrected the seal position.
The r&r is not difficult, 14mm for the line, 13mm swivel socket + extensions for the two nuts that hold it to the bell housing and a 13mm for the bleeder screw. It takes longer to bleed than to r&r it.
uh oh.. Are they ALL bad?? I just opted to replace my perfectly good non leaking slave with one from GM since the entire drivetrain was new front to back. My pedal does squeak when pressing the clutch in.. could it be because of the mcleod unit? Is it hard to remove the slave ? I may just put the original back on and send the new one i got to get fixed.
Sounds like it if they are the OEM looking ones..
You will need an air compressor and a snap ring pliers to fix it..
If you don't want to attempt it, I will fix it for you, but you will need to pay shipping boths ways.
Corvette Store
ZF6 Slave Cylinder Defect Issue FOUND!!!!
I would be 
if I didn't fall victum to their "brain storm"!
