stuck slave cylinder?

[zebra]

anybody ever have a slave cylinder stick in the extended position?

it's been negative outside the last couple days, and when my wife went to work this morning, she called right back saying she got stuck because the transmission was tough to shift in/out of gear. as i drove to get her, i was thinking the new RedLine MT90 fluid might've just been stiff-shifting before it warmed up... but when i got there, the clutch had almost no resistance until the last 1/2" of travel.

i was able to shift enough to get the couple miles back to the house, and upon inspection, there're no fluid leaks & the master cylinder was about 1/2 full. i ended up taking the MC out & it had normal travel & resistance by itself... leading me to the slave.

it's tough to really see through the port for the hydro line, but it seems tight against the pressure plate fingers, and a screwdriver didn't have enough force to spin the throw-out bearing.

could this be a stuck slave cylinder? truck's got almost 135k mi, but i ain't sure if it's the stock clutch or not (bought Nov '19 at 102k, and when i installed the Hurst shifter that winter, i noticed yeller grease pen on top of the trans... meaning it might've been a replacement).

thoughts?



ps - whatever IDIOT designed a freaking $10 plastic single-use retainer clip for the clutch pedal to MC rod connection needs to be punched in the gonads!

 

[4speedfunk]

I had that same thing happen on my 98 S10 years ago. It was the clutch itself. The pressure plate springs suddenly let go. No funny noises or anything…just hardly any pedal.

 

[zebra]

say what?! what would've caused the pressure plate to fail?
not saying it didn't happen or couldn't be the case here... that's just a new one to me.

after talking to 5 different shops today (and everybody's 1st response being, "they made Hummers with manuals?!"), one was able to get it in on Tues. i feel like such a failure for not having the space or tools to drop my own transmission here at the house - had we been at our last place in TX, i'd've probably been done with it by now.

 

[4speedfunk]

say what?! what would've caused the pressure plate to fail?

Wear.

 

[zebra]

of course - it did this again shortly after i deployed a few weeks ago. she's driving my cummins in the meantime, but i'm just gonna drop the trans when i get home & replace the clutch+slave.

any recommendations on replacement kits? seems like the larger 08+ part numbers are hard to look up.
also, does the slave use the same bleed screw as the LS1 clutches? i'd prefer to install a speed bleeder line while i'm in there.

 

[zebra]

without being able to call any dealers, i finally found the Hummer clutch part numbers over on the Colorado/Canyon forum, of all places. the tough part is sifting through the chaff because most companies advertise all Colorado/Canyon/H3 clutches as the same - but they ain't.

the 3.7L H3s came with 24230633: an 11" pressure plate/clutch (bigger than the 10.4" used in the i5 pickups - which is why they upgrade to the H3 parts from that or the 9.x" i4 clutch). it's made by Sachs for GM, LuK, & others... but apparently at some point, they started cheaping out & shipping the bigger H3 pressure plate with the same 10.4" disk as the others.

never fear - 24230637 is apparently the GM part number for the original 11" disk, if you're inclined to purchase it separately (and can find any in stock - one's on eBay right now from down under).

in the aftermarket, it seems South Bend & SPEC both make some upgraded kits in various stages of torque capacity (to the tune of double-to-triple the cost). AutoZone has a decent price for a Sachs kit (including slave & warranty)... but it's definitely the small disk, so i'm currently eying the SPEC SC941 since buying it + slave wouldn't be much more than an OE kit + the "right disk", plus it'd have a good bit more clamping power to manage the mountains we live in & the trails we often drive.

thoughts/experiences?

 

[zebra]

so... if your wife emails you while you're working on the opposite side of the planet saying her clutch lost pressure, and a friend helped her get to a shop who told her they thought the slave was leaking & it'd be $1000 to fix - but you're thinking, "just have her drive your truck 'til you get home & then fix it yourself with much better parts for less than half that price" despite only having hand tools & no lift in the middle of winter... tell that idea to F*** RIGHT OFF!! just pay the shop & be done!

i'm getting too old & broken for this crap! and it turns out the 355 platforms have SIGNIFICANTLY less trans tunnel room to work in than the fullsize trucks. job took all week (granted a couple parts arrived two days late), and i ain't been this sore or close to accidental death in a while.

1st off: i completely forgot you have to remove the front seats & entire center console just to take the shifter off.
2nd: the transfer case does NOT go back in the same way it came out (which was also sketchy when all you got's a floor jack). in addition to the 45° drop being way off balance, the frame crossmember prevents a simple drop-down & requires turning the whole thing 90° & shifting the jacking point while airborne to finagle it down through the gap. putting it back in took every imaginable ounce of creativity & tetris skill because there wasn't no way to jack it up in there off-balance while maneuvering it through the tight space - so after 45min of dancing (almost breaking a finger when it fell once & dumping a pint of fluid everywhere while turning it 69 different ways), i eventually kicked the jack out of the way & just benchpressed it up in there - not caring anymore if it fell square onto my face or chest.
3rd: of the 11 bellhousing bolts, the bottom 9 take ~10 minutes total to remove or install; the top 2 take 45~69min each! i pieced together about 17" worth of socket extensions, attacked them from every conceivable angle/direction, and still could only get one-two ratchet clicks per turn while working blind.
4th: breaking flywheel bolts loose (and install torquing) with hand tools is less than enjoyable and took a hot minute to figure a way to keep the crank from spinning. i ended up reinstalling a pressure plate bolt with a few threads sticking out so the head would seat onto half a floor jack handle - wedging it onto the garage floor. the other half of the jack handle made for a nice cheater on my 1/2" drive.

5th: pilot bushing removal tricks often call for grease or bread... grease is a nightmare to clean up (& expensive), and bread's a waste of good food (my wife buys the fancy stuff). i simply wet some paper shredder scraps & hammered them in with the clutch disk alignment tool; worked like a champ & wiped right out... just took forever.

other than that, it was a straightforward job. as i previously suspected (and seconded by the shop), the slave was definitely the culprit.

turns out - the good news was that the original clutch didn't have 150k miles on it (though the slave probably did). it'd clearly been replaced... but the not-as-good news was that it fell prey to a common blunder i discovered throughout this process: after the 2008-2010 H3s got some transmission beef-up bits to handle its extra weight, they also upgraded to an 11" clutch versus the 10.4" it previously shared with the 3.5 & 3.7L Colorados/Canyons in 2006-2007 (same flywheel & pressure plate - just more friction contact area). the OE-replacement clutches (mostly built by Sachs) didn't keep up & continued selling the 10.4" clutch for all H3s & pickups - which ours ended up with (as evidenced by wear marks at two different radii on our flywheel). the Stage1 SPEC i bought measures 10 7/8" & has a little more clamping pressure than stock, so it should be good.

while i was in there, i decided to build a remote speed bleeder line. it payed dividends on the vette, so i figured it'd be worth trying on the hummer so i could bleed it myself quicker. go figure - nobody in the entirety of the interweb has ever mentioned doing this on (or offering a kit for) the GM midsize trucks... so i found a place that sold all the pieces i needed & built my own. it tucks up out of the way using an existing fuel line bracket.

only oddity so far is that the SPEC instructions never mentioned a need to shim the slave... but it's currently engaging/disengaging at the bottom 1/2" of pedal travel (like a clutch at the end of its life would). i know this design is 'self-adjusting', and i bled the crap out of it last night (~a pint of fluid through), so we'll see how it feels by the end of the 500mi break-in. i REALLY don't want to take all this back apart to space that slave out!