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  1. #1

    Default Fbody Pressure plate with a ZF6

    Perhaps I missed this info during my search of the Corvetteforum, but here's a quick run down of what I'm trying to do.

    I have a 450hp LT1 to go into my Corvette. It's currently in a Fbody I'm returning to stock. The Fbody has a Ram HD clutch kit and Hays Billet Flywheel. I'd like to swap the clutch stuff over with the motor, but I'm reading this from the FAQ area:


    [In stock form, the ZF6 uses a "Pull style" clutch, similar to the LT1-T56 transmission. The only difference is,
    a ZF6 does NOT use a sprung hub clutch disc, but rather uses a dual-mass flywheel with integrated springs between
    the mounting surface and the friction surface. The OEM flywheel sells for nearly $700 US.

    There are a few options for clutch replacement, other than stock. For example, you can change to a singlemass flywheel
    and re-use a OEM type ZF6 clutch kit, OR use fbody clutch components, OR convert to a push style clutch.

    1) If using a Singlemass T56 flywheel out of a 93-97 V8 Fbody (OEM# 10125379), you can use a Fbody sprung hub clutch disc (OEM #12551309),
    but must use the propper ZF6 pressure plate for your transmission. Additionally, the flywheel must be resurfaced .090" for clearance
    with the clutch fork to bell housing. This will only work on 1986+ motors with 1pc rear main seal!]




    I also read this from gtsyellow of CF:

    [When it comes to the pressure plate and throwout bearing, stay with the ones intended for the Corvette. They will fit to these flywheels fine, and will work with either the Corvette or LT1 Camaro clutch disc.]

    But neither place does it state why the Fbody pressure plate can't be used. I know the Fbody LT1 and Corvette LT4 pressure plates are interchangeable, so wouldn't the Ram Fbody one interchange as well?

    Here is exactly what I have:

    http://www.summitracing.com/parts/ra...maro/year/1995

    http://www.summitracing.com/parts/ha...make/chevrolet

    Am I going to be Christopher Columbus'ing this one? Nuckinfuts?
    1994 Z28 383ci - Jake's 4L80 - Moser 9" [LE2 heads and LE cam - 121mph @5500DA]
    1995 Corvette 350ci - ZF6 - Dana 44 [GTP heads - XE503 - RamHD]
    1997 Ram 2500 - tractor motor - duel spinners - chimnie mod

  2. #2
    Long Live the Opti


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    I wish I had some advice for you man, but I don't. I know the ZF had some difference, clutch being one, and had no clue that they were somewhat interchangeable. Just be cautious cobbling parts together in order to make it work, and definitely post up what you find.

  3. #3
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    The pressure plates themselves may interchange, but the throw out bearings are different.


    The left pic is a stock f body throw out bearing, the right pic is a stock ZF corvette throwout bearing.
    Last edited by 94Blackbird; 02-26-2013 at 04:26 PM.
    "Only in the Corps can you put three guys in a room with an anvil and a rubber mallet, come back 15 min later, and the anvil is broken, the rubber mallet is missing, and nobody saw a damned thing!"

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    Quote Originally Posted by Fastbird View Post
    I wish I had some advice for you man, but I don't. I know the ZF had some difference, clutch being one, and had no clue that they were somewhat interchangeable. Just be cautious cobbling parts together in order to make it work, and definitely post up what you find.
    The big differences that I've been able to see are A) flywheel B) sprung (f body) vs unsprung (corvette) hub clutch disc and C) the different throwout bearings. I wish I could find the old pressure plate I have from when I did the last clutch in my car, but the throwout bearings are different from what I remember. The ZF trans may also have a larger diameter input shaft where the TO bearing rides, but I haven't been able to confirm that just yet.
    "Only in the Corps can you put three guys in a room with an anvil and a rubber mallet, come back 15 min later, and the anvil is broken, the rubber mallet is missing, and nobody saw a damned thing!"

  5. #5

    Default

    Good info on the throw out bearing!

    The obvious difference is the dual mass flywheel [which acts as a dampener] and as such the clutch disc is unsprung. The Fbody is essentially the opposite.

    Here is some info I got from gtsyellow about Fbody [single mass] conversion. Mind you this is from 2002:

    [i just looked into the same thing, here's the combo that will work, LT1 camaro singlemass flywheel $100 from salvage yard, ram part number c0083 is a great pressure plate under 500hp, bearing cu656 is also needed, they have a few disc options, a good one is 320m however i just used a slightly cheaper one, the HD camaro disc with a sprung hub, 30% stronger than stock they say and very streetable. i was looking for the part number but can't find it, you just want to ask for a LT1 camaro HD disc if you want to go the same way i did. also i found a nice in depth post someone made i'll repost...see following ALSO make sure your tranny is the same, i have the weirdest feeling 89-93 is one set and 94-96 is slighty different, not 100% sure on this


    Single-mass flywheel conversion

    The ZF S6-40 transmission behind the engine of a ZR-1, as well as that of a LT1 or LT4 Corvette so equipped, comes accompanied by a two piece cast iron "dual mass" flywheel. Camaro's equipped with the LT1 engine however come with a solid "single mass" cast iron flywheel that weighs about half as much. They use the T-56, an entirely different transmission that allows them to utilize this cheaper approach with a conventional sprung hub clutch disc. The Corvette's dual mass flywheel does not allow room for this conventional sprung hub clutch disc, and replaces the function anyway, so a simple solid hub disc is used on Corvettes. The same Valeo pull-type pressure plate is used in both cars, with variations appearing to be perhaps the clamping ring thickness and clamping pressure. Flywheel thickness is about the same, and both use a standard 26-spline transmission input shaft. Except for crankshaft bolt pattern differences between the LT5 and the others, the idea of reducing rotational mass by changing to the Camaro flywheel looks quite possible, but why is the dual mass flywheel there to begin with?

    The dual mass flywheel has a primary and secondary component, the two masses of reference, coupled by a sealed bearing. The primary side fastens to the crankshaft and the secondary side to the pressure plate. The secondary component also acts as the front face for the clutch disc to engage against. The secondary side is allowed to rotate about 20 degrees relative to the primary, on a limited rotationally sprung mechanism. This allows slight rotational freedom between the engine and transmission, to damp mostly no-load idling engine harmonics and smooth engagement. Smaller transmissions don't need such a mechanism since their gears do not significantly resonate with idling engine harmonics. But the inertia of the ZF's components is such that it carries engine harmonics when idling in neutral with the clutch engaged. So to make a world-class car for the masses, GM felt it best to filter out this noise rather than be subject to complaints.

    The problem with the dual mass design is weight, about 38 lbs worth. There is much potential for increased performance by simply reducing the mass of the flywheel, changing to a single mass flywheel. The LT5 has enough low-end torque that the lost flywheel inertia will not impact drivability. Doing so would allow the engine to rev faster, giving the illusion of more power and the reality of faster acceleration. Indeed there is no change in outright engine performance, but the reduction in inertial mass means less of an obstacle to overcome and more efficient use of power.

    If a person wanted to convert a LT1 Corvette to a single mass flywheel, all they have to do is buy a stock or aftermarket replacement LT1 Camaro flywheel and clutch disc, and exchange simply those components alone. But the LT5 has a different crankshaft bolt pattern and so specially made aftermarket flywheels are the only choice. There are three options on the market, produced by DRM, McLeod, and Fidanza. The materials, designs, and philosophies behind each are a little different, but the true difference in performance between them is small and all seem quite durable.

    The single mass flywheel sold by Doug Rippie Motorsports (DRM) is actually a partially processed stock LT1 Camaro flywheel, an undrilled blank that is machined instead for the LT5 crankshaft bolt pattern. This cast iron flywheel incorporates a lightened casting design, and so weighs about 20 lbs. It is the cheapest of the three options at about $300, and has been used with much success. It is also available from Star Performance Engineering Clutches (SPEC).

    The McLeod single mass flywheel is solid aluminum with a removable steel friction surface. This design makes little effort to reduce weight, weighing in at about 18 lbs. One thought about this though is that the mass of aluminum acts as a good heat sink for the clutch disc and perhaps extends disc life. This flywheel is sold by McLeod and LPE, priced around $600-700.

    Fidanza Flywheel Corp. makes a lightened aluminum flywheel, also with a removable steel friction surface. They actually offer to custom anodize the flywheel if desired, with an array of colors from which to choose. This design, much like the stock LT1 flywheel, scoops out the front side in the thick area to yield a weight of about 13 lbs. The craftsmanship is superb and it is popular. Price range is $400-$500, available from dealers like Jeal, SPEC, SGC, and WRP.

    In all cases, conversion requires shorter flywheel bolts due to the standard recessed hub. 7/16"-20 thread grade 8 bolts, 1-1 ¼" length are typical. You'll need eight bolts for an LT5. Star or flat washers are recommended, especially with aluminum, and Loctite 262 threadlocker should be used in all cases.

    The function of the recessed hub is for the use of a sprung hub clutch disc. A sprung hub disc is technically mandatory based upon any solid flywheel clutch design, and highly suggested, but many have done this conversion while retaining the Corvette's original solid hub disc. It is a good idea to use a sprung hub to allow for some freedom in rotation between the engine and transmission, much like that of a dual mass flywheel, but primarily it will minimize shock and provide smoother engagement. Sprung hub discs don't have much impact on the transfer of engine idling harmonics.

    In selecting a sprung hub disc to use, there are many choices available and care must be taken. The disc must be originally intended for the LT1 Camaro/Firebird to properly work with the pull-type pressure plate. The stock LT1 disc's hub is too large to clear McLeod and Fidanza smaller recessed hubs without custom machining, but is of course intended to be used with the DRM flywheel. Centerforce, McLeod, Clutchnet, and SPEC produce smaller sprung hub discs for the LT1 Camaro application that will easily clear the smaller recessed hubs. These have six small hub springs and can easily be differentiated from the original with its five springs. The stock disc can be bought from SLP for $90.

    When it comes to the pressure plate and throwout bearing, stay with the ones intended for the Corvette. They will fit to these flywheels fine, and will work with either the Corvette or LT1 Camaro clutch disc.

    The price for converting to a single mass flywheel is amplification of no-load engine harmonics, the sound of marbles rattling together when the engine is idling with the transmission in neutral and the clutch engaged. How much of a problem is this? In my experience, and that of most others, it is not a problem at all. With the radio at normal listening level, the noise typically can hardly be heard. Some however seem to have much more significant noise problems. It doesn't seem specific to a certain flywheel brand or material. Changing to a sprung hub clutch disc when converting to single mass is a good idea, and could have an impact on these problems. But I believe it is more the result of engine, clutch, or transmission imbalances or other irregularities, or perhaps simply a low idle speed- or sensitive person.

    Though I don't feel it is warranted, the transmission noise at idle can be reduced or eliminated by increasing idle speed to 1000 RPM, and/or changing to a synthetic transmission lube. Of course another option for similar gains without noise would be an aluminum dual mass flywheel, but the effort and cost are really unnecessary. A single mass flywheel and sprung hub disc are an effective, minimally invasive modification that will leave you asking why you didn't act sooner, I highly recommend it!
    ]

    Here is what I've got from the FAQ area:

    [ZF6 Clutch Specifics:

    In stock form, the ZF6 uses a "Pull style" clutch, similar to the LT1-T56 transmission. The only difference is,
    a ZF6 does NOT use a sprung hun clutch disc, but rather uses a dual-mass flywheel with integrated springs between
    the mounting surface and the friction surface. The OEM flywheel sells for nearly $700 US.

    There are a few options for clutch replacement, other than stock. For example, you can change to a singlemass flywheel
    and re-use a OEM type ZF6 clutch kit, OR use fbody clutch components, OR convert to a push style clutch.


    1) If using a Singlemass T56 flywheel out of a 93-97 V8 Fbody (OEM# 10125379), you can use a Fbody sprung hub clutch disc (OEM #12551309),
    but must use the propper ZF6 pressure plate for your transmission. Additionally, the flywheel must be resurfaced .090" for clearance
    with the clutch fork to bell housing. This will only work on 1986+ motors with 1pc rear main seal!

    2) If using a Singlemass 4+3 flywheel (OEM# 14088646), you can use an OEM type ZF6 clutch kit, but due to the lack of a dual mass flywheel
    OR sprung clutch hub you will get some gear noise.

    3) You can use a Singlemass 4+3 flywheel with an OEM type 4+3 PUSH clutch, but NOT with the ZF6 hydraulics!
    You need to convert to a hydraulic throw out bearing (such as Howe 82876 for Black Tag ZF6 with a 1.375" TOB). LD85 has completed
    this swap and has added the following information:

    "Essentially, I use a 4+3 FW , PP and Disc, .100" spacer between the BH and Block, and a Hydraulic Howe Push Type slip on TOB,
    a Wilwood 3/4" bore Master Cylinder, and a Clutch Pedal travel stop."

    Expect to pay about $160 for the TOB, $160 for the master cyl, and another 40-50 in materials to make the spacer + pedal stop.


    AGAIN, A DUAL MASS or A T56 flywheel will only work on a 1986 AND UP MOTOR WITH A 1PC REAR MAIN SEAL!]


    I've also read conflicting information about the throw out bearing being different between the black tag and blue tag ZF6's transmissions. It seems that Carolina Clutch is a place many people get referred to for clutch kits, etc for C4 Vettes. I'm hoping that calling them tomorrow will yield more results than I got from Ram today.
    1994 Z28 383ci - Jake's 4L80 - Moser 9" [LE2 heads and LE cam - 121mph @5500DA]
    1995 Corvette 350ci - ZF6 - Dana 44 [GTP heads - XE503 - RamHD]
    1997 Ram 2500 - tractor motor - duel spinners - chimnie mod

  6. #6
    "The Hammer"


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    I think where the confusion is coming is because the black tag trans has a larger input shaft diameter than the blue tag. Black =1.375 Blue= 1.311. As far as I can tell the throwout bearings are the same though.
    "Only in the Corps can you put three guys in a room with an anvil and a rubber mallet, come back 15 min later, and the anvil is broken, the rubber mallet is missing, and nobody saw a damned thing!"

  7. #7

    Default

    Hmm, more good info that I don't have to measure with a caliper later, thanks.

    What's the T56 diameter?

    I sure hope this works out, the only possible hitch of this whole swap is with the clutch stuff. Everything else is cake.
    1994 Z28 383ci - Jake's 4L80 - Moser 9" [LE2 heads and LE cam - 121mph @5500DA]
    1995 Corvette 350ci - ZF6 - Dana 44 [GTP heads - XE503 - RamHD]
    1997 Ram 2500 - tractor motor - duel spinners - chimnie mod

  8. #8
    "The Hammer"


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    Sorry, I don't have that information.
    "Only in the Corps can you put three guys in a room with an anvil and a rubber mallet, come back 15 min later, and the anvil is broken, the rubber mallet is missing, and nobody saw a damned thing!"

  9. #9

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    No problem man, you've been more help than anyone else so far.
    1994 Z28 383ci - Jake's 4L80 - Moser 9" [LE2 heads and LE cam - 121mph @5500DA]
    1995 Corvette 350ci - ZF6 - Dana 44 [GTP heads - XE503 - RamHD]
    1997 Ram 2500 - tractor motor - duel spinners - chimnie mod

  10. #10
    "The Hammer"


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    Quote Originally Posted by Bersaglieri View Post
    No problem man, you've been more help than anyone else so far.
    I am swapping a ZF into my trans am.
    "Only in the Corps can you put three guys in a room with an anvil and a rubber mallet, come back 15 min later, and the anvil is broken, the rubber mallet is missing, and nobody saw a damned thing!"

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