[ArthurJGuy]

I pulled the transmission yesterday and installed a brand new F-body slave, ensured that everything was torqued properly, and took some measurements.

Pressure Plate to Bell 2.280
Slave to Trans 2.110
Difference 0.170

I see a .055 shim in my future. Thanks for laying this shit out KtG

 

[erock]

Konnie, just getting to respond to this, I guess better late than never. Anyway, amazing and so simplified no one here that sees this should have future clutch problems that remain a mystery. One thing though I would like to point out is about heat and expansion. In your examples you showed how the clearance of disk to PP diminished in just a 1/16 off from the TOB spacing, imagining what that difference would be under operating temperature when the parts have had a chance to expand. As mentioned, the examples prove the obviousness of most cases inability to shift properly ,IE, like a "CEO" or a "Boss" .

 

[Konnie the Goat]

Bump to settle all this 'i need a new master' talk. Stock master is fine. the aftermarket just gives you a harder and slightly shorter pedal. Which has its own value if that is your taste, but it wont fix a damn thing.

 

[ArthurJGuy]

Bump to settle all this 'i need a new master' talk. Stock master is fine. the aftermarket just gives you a harder and slightly shorter pedal. Which has its own value if that is your taste, but it wont fix a damn thing.

100% Fact.

I drank the kool-aid, I didn't like it and it didn't give me super powers.

 

[DSMinVA]

Figured I would add my experience too.
Thought I had a master cyl issue and almost bought the tick master but after LOTS of reading on here decided to give the shimming and new lines a try instead since I had a new LS7 clutch in the garage waiting.

Turns out my issues were a leaking slave cyl, and broken TOB.
New LS7 clutch/flywheel, new slave cyl, stainless braided and heat wrapped lines, and not a problem since. I checked for proper shim size and found I didn't need one with my setup. Cost was alot less than a new master cyl too since I already had the clutch. YMMV.

 

[Stlakid]

Just a thought because I have seen it mentioned a few times here. From what I have gathered if you use the LS7 or an equivalent stock type replacement cover assembly you will not need a shim. EVER. The fingers can adjust almost 1/2" during use. That is why the clutch pedal is right off the floor after install; they have not adjusted to the assembly yet.

 

[ArthurJGuy]

KTG any input as to what commonly leads to a leak in the slave?

I just pulled out a slave that is less than 6 months old with less than 5k miles on it and the entire bottom of it is stained from my clutch fluid. I didn't expect one to fail that soon.

 

[DSMinVA]

KTG any input as to what commonly leads to a leak in the slave?

I just pulled out a slave that is less than 6 months old with less than 5k miles on it and the entire bottom of it is stained from my clutch fluid. I didn't expect one to fail that soon.

Do you have LT headers?
Its my beleif that the LT's are boiling the clutch fluid, and in turn essentially melting the rubber seal of the slave cylinder. (and the rubber flex line, thats why the fluid turns black) I'd put money on this, as I didn't have any clutch issues untill I put the LT's on.

FWIW - I put in a used LS7 assy with around 1500-2000 miles on it. Still checked all measurements. Its great that everyone says stock clutches don't need shims, but it only takes 5 minutes to check with a few straightedges. Don't skip out on this step, seriously - it costs no $$ to do, and you can rest assured you have done it right.

 

[ArthurJGuy]

I have coated headers, an insulated braided line, and I'm running a fluid with a much higher boiling point.

 

[svede1212]

Just a thought because I have seen it mentioned a few times here. From what I have gathered if you use the LS7 or an equivalent stock type replacement cover assembly you will not need a shim. EVER. The fingers can adjust almost 1/2" during use. That is why the clutch pedal is right off the floor after install; they have not adjusted to the assembly yet.

Any hydraulic clutch system normally adjusts itself.

It works just like your brakes. On your brakes the brake pad rides right against the rotor. When you press the brake the pistons extend and push the pads onto the rotor. When you take your foot off the pressure of the pad pushes back to its original point of just off the rotor. When you change pads you push the pistons back to get the thicker pads on. When you first press the brakes the pedal can go right to the floor until the system "pumps up" with fluid from the reservoir. From then on the pedal is in the same place even when the pads wears down and the piston is out much further.

The clutch system works the same way and as long as it's bled properly you "pump up" the system until the piston presses against the PP fingers. When you push the pedal again the piston extends and presses the PP fingers in. When you let off the fingers push the piston back reversing the flow of fluid. The reason for the shim isn't because the system can't adjust. It's because the throw of the piston is pretty short. If you reach the "end" of the normal throw and keep pushing the piston can blow it's guts when it passes the end of the seal.

Part of the high RPM shift problems are the stock clutch itself. The PP finger springs aren't strong enough to overcome centrifugal force at high RPM. The new stronger clamping PP does and viola the problem is fixed. The stronger PP springs also cause there to be more pressure in the system to have it overcome the springs and that shortens the life of the slave.

 

[DSMinVA]

Great post Svede!

Arthur - lemon slave maybe? Or what Svede said, maybe it blew its guts out from over travel. What clutch are you running?
EDIT- just saw you shimmed allready, so probably no over travel. Dunno

 

[ArthurJGuy]

Either it was a lemon slave, or smurf this slave. I'm just annoyed that it failed so soon. Lucky for me its a free warranty exchange.

 

[svede1212]

Either it was a lemon slave, or smurf this slave. I'm just annoyed that it failed so soon. Lucky for me its a free warranty exchange.

Hell it ain't the cost of the slave. It's the sore back from a day jammed under my car. Of all the parts there is an aftermarket for this is one that people would gladly pay 2-3 times as much to get a more robust slave. Look what people pay for radiators that take 45 minutes to change just so they don't have to do it again. It's odd with all the Corvettes, fBods, GTOs, Monaros, Vauxhalls, SS's and whatever else that nobody in 15 years has made something.

 

[Konnie the Goat]

The slaves we have shouldnt even work if you want my honest opinion. The sealing of the thing is shit. The dust seals might as well be holey condoms. and the piston seal, that figure 8 bastage that holds all the load and does all the work, could probably use a metal core. The only thing saving it is the TOB rides on plastic which is a thermal insulator.

Should still last longer than yours did. So I move for lemon. They are cast parts and the piston bore is machined. Hecho en Mexico, so Im willing to bet the tolerances are shit. I'd like to get a few dozen and mic them. Just for curiosity.

 

[DSMinVA]

I'd like to get a few dozen and mic them. Just for curiosity.

And your just the guy to do it!

 

[GTO9090]

I realize I am late to the party but this is such an informative thread, I am surprised it has sat for so long. I am in the process of putting my transmission back together but am reserved because of all the back and forth about proper separation of the pressure plate.

I got these numbers from Konnie's actual measurements. Can someone check this math? Why does he only get 0.3125" of travel in his video labeled "stroke with proper spacing"

Slave Cyclinder
Inner D = 1.43, A1 = 1.606
Outer D = 1.85, A2 = 2.688
A2 - A1 = 1.082 in^2 cross section

Master cylinder
D = 0.750, A = 0.442
Stroke = 1.25"
Volume = 0.5525 in^3

Because of an incompressible fluid, fluid volume movement of the master translates to equal fluid volume movement of the slave
Vm = Vs
(1.082 in^2) * slave stroke = 0.5525 in^3
Slave stroke = 0.510 in^3 assuming a full 1.25" of master cylinder stroke

Another thought; as long as the slave cylinder does not hit full extension (which is like 0.930"), shouldn't you always get the same slave stroke and therefore the same separation? It is a sealed hydraulic system and the volume of fluid the master pushes to the slave will be the same regardless of if the slave cylinder starts at the base or 3/8" from the base. There just seems to be a lot of debate on whether or not 0.0625 or 0.200" spacing is better between TOB and PP fingers. Should it not all stroke the same and therefore cause the same separation? I believe that is why it is considered self-adjusting as long as your hydraulic system is full and has no air bubbles.

 

[GTO9090]

Just for the sake of accuracy, I also cut a slave cylinder up and got the following dimensions measured with a caliper. Inner D of the slave is 1.433 and outer D is 1.870 giving a cross sectional area of 1.130 in^2. I'm highly confident in these measurements.

This would mean a stock MC at a full 1.25" stroke and 3/4" bore will move the slave cylinder 0.489 in
The aftermarket Tick MC at 1.1" stroke and 7/8" bore could then move the slave 0.585 in

Since Koni's video only shows 0.3125" of stroke with the stock MC either 1) there was air in the line being compressed, 2) the stock MC does not actually give you the full 1.25" of stroke, or 3) his bench top setup wasn't stroking the MC fully.

 

[yellow]

Another thought; as long as the slave cylinder does not hit full extension (which is like 0.930"), shouldn't you always get the same slave stroke and therefore the same separation? It is a sealed hydraulic system and the volume of fluid the master pushes to the slave will be the same regardless of if the slave cylinder starts at the base or 3/8" from the base. There just seems to be a lot of debate on whether or not 0.0625 or 0.200" spacing is better between TOB and PP fingers. Should it not all stroke the same and therefore cause the same separation? I believe that is why it is considered self-adjusting as long as your hydraulic system is full and has no air bubbles.

I would agree with this statement. Fluid fills in the space in first stroke and stays there forever after. From this point on, throw out bearing is always in contact with PP fingers.

 

[yellow]

Since Koni's video only shows 0.3125" of stroke with the stock MC either 1) there was air in the line being compressed, 2) the stock MC does not actually give you the full 1.25" of stroke, or 3) his bench top setup wasn't stroking the MC fully.

He is using F-body slave cylinder. I don’t think it’s the same as GTO slave.

 

[Nothubertjfarnsworth]

He is using F-body slave cylinder. I don’t think it’s the same as GTO slave.

It's the same except for the fittings.