Slave cylinder shimming

Discussion in '2005+ Mustang GT 4.6L Tech' started by ghunt81, Feb 13, 2020.

  1. ghunt81

    ghunt81 New parts on old junk! S197 Team Member

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    Measured all my stuff yesterday with the slave installed on the transmission, clutch/PP installed to the flywheel and everything torqued to spec. I'm seeing about 2 11/16" from the bellhousing face to the TOB face, and about 3 1/8" from the block plate to the PP fingers. So, a difference of 7/16".

    So I'm guessing I need a shim but what I'm not clear on is how much of a shim. I've seen that you're supposed to have around 1", but I've also seen where people said the actual travel is only 1/2"...so I'm not totally clear. Now granted I didn't measure the stock stuff before I took it out but this is an OE replacement clutch kit so everything should be similar and it had no shims. I will say that on the stock clutch you had to push it all the way to the floor to make sure it was completely disengaged. Never really had any problems shifting though.

    Would a a single 3/16" shim be enough?
     
  2. rocky61201

    rocky61201 forum member

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    Sounds like you could get away with using 1 spacer. I'm guessing you could use none or even two spacers.

    Hold your slave cylinder in your hand and compress it and measure the travel. I'll bet its a tad over 1 inch. If you put too many spacers in there and get preload longer than 1 inch you'll never get the transmission installed flush against the engine block face because you've bottomed out the slave cylinder. So just make sure you DONT go over 1 inch. Make sense???

    Also make sure you pick up 2 longer than stock M10 bolts to compensate for the spacers.
     
  3. ghunt81

    ghunt81 New parts on old junk! S197 Team Member

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    I'll have to do some more measuring to check that...at any rate I found a place on ebay selling 3/16" thick, 4-1/2" round steel discs for super cheap so I will make my own spacer. I bought two discs just because they were only $2.50 each and I wasn't sure if I would need one or two. I'm thinking one spacer will probably be a good idea though. Thanks for the input!
     
  4. JeremyH

    JeremyH 3V Fuel Guru S197 Team Member

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    What is the clutch/flywheel setup? Unless your running something unique, different year parts etc, no 3v specific clutch would need the oem slave shimmed.
     
  5. ghunt81

    ghunt81 New parts on old junk! S197 Team Member

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    It's all OE replacement but as I said...only seeing 7/16" of engagement at the slave cylinder which doesn't sound like enough. And I did occasionally have some difficulty with upper RPM shifting. I'm going to try one 3/16" shim.
     
  6. GlassTop09

    GlassTop09 Member

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    Curious as to how that will come out as, if my math is correct, the 1 3\16" shim should make your total TOB preload 5\8" instead of the 7\16" you have currently, yes? So this means that you'll only have 5\8" of total usable TOB stroke before the TOB bottoms out (TOB at full extension, which is where it was when you took the initial measurement.....at least my assumption that it was at full extension). I'll assume that you didn't measure the existing clutch assembly while still bolted up to get this info prior disassembly...……...

    The way I understand this, the less TOB preload, the closer the clutch release point is to the pedal travel hitting the floor (or the clutch disengagement point if you prefer). The more TOB preload, the further the clutch release point is from the pedal travel hitting the floor (or clutch disengagement point if you prefer) w\ 1" representing the max TOB preload possible.

    The problem is knowing\figuring out where the minimum total TOB preload should be to provide full clutch release when system is fully bled out & pedal is fully depressed (car doesn't try to move when shifting into gear) to the floor as this point will\can be slightly different from 1 clutch assembly to another...even of the same manufacturer & class (due to manufacture QA\QC tolerance. Example: a 5% height tolerance means a difference of almost 1\16" of TOB preload...question is, which direction? Shorter or longer?) If this is\was known then you can\could adjust for pedal height\travel preference....

    Just looking at your measurements my gut says that a final min total TOB preload of 3/4" (so a 5\16" shim) is more ideal IMHO but I can't say this from any level of experience (only using the math to work this from the std of 1" total TOB preload) as I have never installed a clutch assembly in a vehicle using a non adjustable hydraulic master\concentric slave TOB system, only mechanical linkage type systems where you can adjust for all of this post install so not as big of a deal as these are.
    That's a lot of work to install the trans then when you get the clutch all fully bled out you find the clutch won't fully disengage when pedal is depressed to the floor...………….

    I know this is more work to do at this point but before I would go ahead I would pull the new stuff off, remount the old clutch disc & PP then get measurement of this height to then make a comparison to the new stuff to then make a better decision as you were used to what the old stuff was measuring out to so it would seem to me to start there then make any adjustments so that you won't have to do this work more than once.

    Just a suggestion...………...

    All I do know is that all manual clutch packages for this 4.6L 3V aren't made to hit the exact same total TOB preload measurements but when using the OEM flywheel (or an aftermarket flywheel that measures out to exactly the same height as the OEM unit) the odds should be better but also personal preference will also dictate where the total TOB preload is set & this may be different from where the clutch manuf may have designed a particular package to fall....thus why you should measure for this IMHO.

    Hope it all comes out to your liking the 1st time..........................
     
  7. JeremyH

    JeremyH 3V Fuel Guru S197 Team Member

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    Do not shim it. Unless you want to take it back apart prematurely from excessively preload after bleeding. Put in the oe parts bench fill the slave, pedal bleed the rest. But a few hundred miles on it. Then think about taking a measurement if it butters your bread, otherwise leave it alone.

    There is zero reason to shim a oe setup.
     
  8. JeremyH

    JeremyH 3V Fuel Guru S197 Team Member

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    Btw the problem with upper rpm shifting is rarely clutch related. It's due to motor/trans torque rotation relative to a non driveline (body) mounted shifter.

    The oe hydro motor mounts are shot around 75-100k. Get some poly or prothane motor mounts thats step 1 to helping everything in line when high rpm shifting.

    You seem to be bumbling around in the dark with your threads, tons of experience and threads to look through on here.
     
  9. 1950StangJump$

    1950StangJump$ forum member

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    When I had the T56 Magnum and RST installed by JPC, I forgot to ask them if they had to shim it. I wish I had for my own knowledge.

    With that clutch, when I start to press the pedal, it begins to disengage within about 1/2" from the top - way, way high. But, once the clutch is on the floor, and you begin to release it, you can feel it catching the car by about 1/3 of the way up the travel - as opposed to not catching until the top. Is that the nature of a dual clutch vs OEM?
     
  10. ghunt81

    ghunt81 New parts on old junk! S197 Team Member

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    Well...this is partly what I'm basing my shim idea on. Granted I did not measure the old stuff, but the OEM clutch was a Valeo and probably identical to this Luk I'm putting in. The OEM slave is basically identical and has the same piston travel of roughly 1 1/4" from fully compressed (also FWIW, the Luk slave I got originally had a Ford logo and part number on it that were machined off). At any rate on the stock clutch I always noticed the pedal had to be on the floor to completely disengage the clutch, or even to activate the neutral safety switch to start the car, which was always a bit of a pet peeve of mine. If one shim moves it up a bit that would be fine with me.

    I'm sure there is but that information is not always easy to find, because a search returns a lot of unrelated stuff. Also, THIS particular topic- the information seems to be all over the place. Shim, don't shim...this whole thing has been needlessly frustrating. I don't see how I could have excessive preload on the slave if I'm only measuring 7/16" engagement right now and it has 1 1/4" of travel.
     
  11. eighty6gt

    eighty6gt forum member

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    my shifting was partially clutch related, but was from worn parts.

    shimmed my slave 3/8" (dwg attached)

    works a treat

    DOB knows. He's spoken with Ford, they allegedly use his methods for preload.

    The slave should be pre-loaded correctly.
    -Measure from the block/trans mounting surface to the tips of the "finger springs" on the pressure plate.
    -Measure from the mounting surface on the bell housing to the "face" of the slave.
    -You're going to need to account for the thickness of the "bell housing spacer/plate" into one of the above measurements. Or just put in on the block and do the first measurement with it already on there.
    -Take your two measurements and see how much pre-load is being placed on the slave when the trans is bolted up. You want about one inch.
    -Shim for goal
    Depending on a lot of things I have run shims anywhere from 1/8-1/2" to get things right.

    3_8 spacer TR3650.idw.png
     
  12. ghunt81

    ghunt81 New parts on old junk! S197 Team Member

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    Did you have any problems with the clutch line connection using a 3/8" spacer?
     
  13. rocky61201

    rocky61201 forum member

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    Everything I've stated about preload and shimming started when I found that DOB thread. He is the guy that created the supercharger manifolds we love so much. So yea I trust the guy too.

    FWIW I have an Exeedy billet steel flywheel, an LUK clutch and ToB I got off rock auto. I have two RAM .156 inch thick shims I got from LMR.com. Got my preload just under 1 inch. Probably about 7/8. I forgot what I measured back then. Been installed for about the past year and 25k miles. Zero problems. I like it, nothing is broken yet, and engagement is right in the middle of pedal travel. I'm not saying it will work for you. Just putting that out there since you started this thread. I also have BMR motor mounts and the blowfish shifter bracket that helped out way more than the shims.

    Oh yea - no issues with connecting my braided clutch line either.
     
    Last edited: Feb 19, 2020 at 4:32 PM
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