I have vastly different hydraulics than most of you but no matter. last weekend I installed a quick disconnect coupler in my clutch line. This part is supposed to be for clutches and suchhttp://www.howeracing.com/drivetrain...vecylinder.htm for a look... I have a problem like I thought I would after I installed it.. The master moves enough fluid to actuate the valve therefore stopping flow... I recall that the ls1 hyd have a similar valve in them so you can seperate them without fluid loss. When pressing the pedal it only happens if I do it quick..When I let up it doesnt have to be real quick to happen. The hotter the fluid the easier it happens to the point that it sticks to the floor. This sounds A LOT like the problems you guys are having..It happens more on the upswing because your lowering the pressure on the master side. On the downswing your building pressure so its more equal on both sides of the check valve..
Thoughts...........

 

Well last night the valve caused overextension and blown seal of my hyd throwout...Guess im taking my tranny out AGAIN AND the valve.