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Has anyone else had a difference between original and GM replacement C5 Z06 clutch slave fully depressed without spring measurement? Setting up my new RST clutch and my new GM slave sits down in the base .110" more than the original slave, both with the spring removed as recommended. My total clearance measurement with that additional makes .390" requiring a .140" shim to get under the recommended .250" maximum. That is a lot of shim and gets the slave out of the area where it seats itself on the machined base. The slave is the same height overall so I need to know if I need to add the additional .110" to the balance of the measurements or not.
Help!! .110 shorter when depressed Same overall height
My opinion: if they are the same height when fully extended (i.e. with springs put back on), it's fine as-is and doesn't need a shim.
The part that bothers me is if the travel is different, because if the slave travel/stroke is longer the clutch may not disengage if left at the same distance as stock.
I'm no expert but did a clutch and slave recently. New slave was very slightly different than old (both OE parts, original 2004 and GM replacement from Tick). Not enough to make a difference, iirc it was different when compressed by 0.05" and the compressed height still fell in the acceptable range for installation.
The part that bothers me is if the travel is different, because if the slave travel/stroke is longer the clutch may not disengage if left at the same distance as stock.
The pressure plate is what dictates the positioning of the slave. A longer stroke of the slave is inconsequential so long as: 1) the pressure plate is able to return to its natural state and not have the slave bind up before that point (clutch pedal release); 2) the top of its stroke isn't too long (too long would mean overcompressing the pressure plate).
If you've already demonstrated that both slave cylinders are the same height at the top of their travel, then it doesn't matter that your new one has a longer stroke at the bottom of its travel.
At the bottom of travel the slave will end up wherever it ends up based on the pressure plate, and the slave's spring will keep the TOB from traveling any lower.
Also in general, stroke length will be dictated by the hydraulics (when it's not otherwise limited mechanically). It's probably fair to assume that the bore size of your old slave and new slave are the same, so their travel will be comparable for a given pedal press.
Update: Although I had the bleeder open when I measured the original slave, I tried tapping the TOB with a hammer with the bleeder open as well. Guess what, a good bit of sludge pushed out and now the 2 slaves measure the same. That issue solved. However I will now need to shim a good bit to get to under .250" with a current clearance of .405".
a good bit of sludge pushed out and now the 2 slaves measure the same.
Good catch! Since a Tick shim pack includes .055, .115, & .180 shims I’d say stick with the factory’s recommendation and shim as required. My clutch was not shimmed, and the engagement is closer to the floor than I really like.
GM Replacement Slave TOB Measurement
