Type of Pressure plate?

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Alaskaman, Dec 5, 2018.

  1. Alaskaman

    Alaskaman Registered User

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    Hello to all of you great IDI owners.

    Well it's time to replace my slipping Clutch. I have a 1993 7.3 factory turbo with a 5 speed transmission.

    Besides pulling the transmission and looking, is there a way to know if there is a Dual Mass or Solid Flywheel?

    With that being said, I understand that some replace a Dual Mass with a Solid Flywheel if the Dual mass is installed. I don't know if some folks put a Dual Mass to replace a Solid. I'm up for some input on the Pro's & Con's of each.

    Thank you in advance & Merry Christmas.
     
  2. Macrobb

    Macrobb Full Access Member

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    Dual mass flywheels SUCK. Plain and simple. If anything is slipping with a DMF, it's probably the flywheel itself, not the clutch attached to it. (The problem is the "torque limiting" friction disk inside the DMF itself).

    Go LuK SMF.

    How can you tell? Pull inspection cover off the underside of the trans, where it covers the flywheel. With trans in neutral, you should be able to freely rotate the pressure plate with your fingers, by 3/4" or so. If you have no movement, it may well be a SMF.
     
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  3. Alaskaman

    Alaskaman Registered User

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    Thank you for the input. I don"t have any experience with a DMF. It never slipped with a heavy load, but it would intermittently slip without a load at higher RPM's going uphill. From what you said about the DMF, I think I may have one.
     
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  4. 79jasper

    79jasper Chickenhawk

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    Dmf flywheel in itself cant slip...
    There are stops inside.
    If you search post from the late towcat, you can find his many posts on the dmf vs smf.

    Sent from my SM-N960U using Tapatalk
     
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  5. Macrobb

    Macrobb Full Access Member

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    Yes, they can.
    I have one that *did*.
    When I first got the truck, it was just fine. Never slipped.
    Then, I took it on a 3 hour journey, it got hot... and started slipping. Could only give it maby 1/3 throttle before it started slipping.
    Let it cool down, it was fine except when I'd floor it.

    I figured it was the pressure plate/friction disk. So I ordered a new one, pull the transmission and find that the old disk... looked fine.
    I replaced it anyway. Put everything back together and... still slipped when floored. Same exact level of power.

    I got under there with my MIG torch and simply welded the two pieces of DMF together with 4 1" welds.
    Fire it up and... No more slipping. *very* noisy at idle, though.

    I then ordered a LuK SMF, installed it, and never had a problem since. And it's quiet.
     
  6. 79jasper

    79jasper Chickenhawk

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    I guess you could break through the stops.
    I'll have to find the dmf dissection thread.

    Sent from my SM-N960U using Tapatalk
     
  7. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    If you are dropping the clutch I could see it possible to break the ears off the dmf and it would just free spin, but that’s a mechanical failure that’s not part of the design of the flywheel. The flywheel isn’t torque limiting, it just has moving parts that will break under a lot of load, just like a trans with a weak 2nd gear. It’s not a torque limiting gear, it’s just a weak design.
     
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  8. Alaskaman

    Alaskaman Registered User

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    Gentlemen, Thank you for your input and knowledge. I'll go look up information from the late TowCat put a plan together and get this slipping fixed.

    Thank you again for sharing your knowledge.
     
  9. franklin2

    franklin2 Full Access Member

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    The original DMF Ford installed is torque limiting. It has two sections to it. The outer section with the friction surfaces and the springs is for noise. There is a center section in the middle of the flywheel for torque limiting, and it can slip when you guys turn these trucks up.

    Below is a picture of the clutch packs, you can see the large section with the little stops on it where the springs go, and you can see the smaller center section, the one with the slotted piece.

    [​IMG]
     
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  10. franklin2

    franklin2 Full Access Member

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    To the original thread starter, Ford did not install these dmf flywheels to aggravate all their truck owners and make them spend gobs of money years down the road, though it would seem that way. They installed the DMF system because of noise generated in the zf 5 speed by the diesel engine. Most likely you will install a conversion kit that converts your truck to a solid flywheel, if you find a DMF if it is pretty expensive. But be warned you may get some noise at idle and certain conditions from the trans. It will sound like it has gravel in it, but there is not a thing wrong with it. Some trucks are louder than others, but you will get some noise from it.
     
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  11. Macrobb

    Macrobb Full Access Member

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    They also can slip at lower power levels when hot or worn, but yes, turbo power levels are much harder on the silly things.
    In the case of my '93, even at 250RWHP(more than you can get with a cranked up pump) I had no slipping issues... *until* I finally got the thing hot by driving 3 hours with an unloaded trailer.
    (I'd driven with a /loaded/ trailer multiple times before that, but only 1 hour or less without issues).

    edit:
    Also, with my '92 - When I picked it up, it "needed a clutch". It slipped at barely above idle, though would get to 60 if you were really careful.
    Pulled the DMF(which had been replaced maby 10 years before? It was an aftermarket one)
    The friction disk was fine, the ball bearings were falling out of the bearing race, and I'm pretty sure the torque limiter was the failure point there.
    And that truck hadn't been turned up much, considering it still had the torque limiter screw in stock spot and still had fuel screw adjustment to be made(made like 150rwhp on the dyno a bit later with maxed fuel screw, then cranked the torque limiter back out and made 200rwhp)


    Yeah, true. Part of the solution is that the LuK SMF kit has two rows of springs in it; it seems to make a big difference.
    The other thing you can do is add an extra quart of ATF to your 5-speed(through the top). This helps quiet it down, and I've never heard of anyone having issues from it.
    Also, adjusting your idle speed a little can have a big impact - if it happens to hit a harmonic at idle, that's when you get the really bad gravel noise at idle. Adjust it up or down so it doesn't hit that speed, and it'll quiet it down more.
     
    Last edited: Dec 8, 2018
  12. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    I’m afraid you are misunderstanding how these flywheels work, they are not designed to limit torque, they are designed to allow a small amount of movement to dampen vibrations to keep the transmission quiet. The ears on the discs I have circled in red are allowed to move but are stopped by the springs. If they were a clutch, they wouldn’t be limited in how much they could move, they would be able to spin 360*

    If the ears are broken off, or the springs are gone then it could free spin since nothing is limiting their travel. 7676AA67-4C0E-406B-9BDD-2AC42A51B917.jpeg A629B38E-259C-4D05-A3E2-618C6F03447D.jpeg F12F9655-72A2-4E17-B428-A5FC446A6518.jpeg
     
  13. Macrobb

    Macrobb Full Access Member

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    You can see the friction material in your first image, as a gray ring. That corresponds with the shiny ring at the bottom of the picture. No, those tabs and springs don't slip - it's the output flywheel part(bottom) slipping against the friction material(top). The force against that is produced by the 6 bolts holding A to B - less force = less total transmitted torque.

    You can also see that those parts have been slipping against each other now - look at the wear marks in that friction material, and how shiny the ring at the bottom is.
     
  14. 79jasper

    79jasper Chickenhawk

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  15. franklin2

    franklin2 Full Access Member

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    It's been awhile since I had mine apart, I did the Lucky Mod to mine. But you will notice when you take it apart, there is no solid bolted connection between the center hub and the part you are looking at with the ears and the springs.
     

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