Flexplate and converter issue

Discussion in 'The "Juice Box"' started by Dr. Evil, Apr 1, 2018.

  1. Dr. Evil

    Dr. Evil Silver Level contributor

    I ran into an issue tonight trying to bolt up my trans.
    The setup...
    Stockish 455 with original flexplate.
    Rebuilt th350
    Hughes Gm30 converter.
    We broke the motor in on a stand a few weeks ago, no issues or wierd vibration.
    The converter has a ring with 3 holes in it instead of the 3 pedestals like a stock converter has. The ring is making contact with the edge of the weight on the flexplate preventing it from seating fully against it. I have a spare flexplate from a 70 455 and it looks exactly the same only a bit thinner. Both are slightly cupped, or concave.
    Looking at the marks on them from the stock bolts and converter, the weight faces the transmission. Is this correct?

    Not only is the ring on the converter hitting the weight but it's very tight. I'm sure the converter is fully seated. Even if it didn't hit, it would be making contact instead of having to pull the converter up to the flexplate. I've not done a lot of these but there is usually a small gap between the two and you "pull" the converter up to the plate.

    It's almost as if I have the flexplate on backwards but I'm sure that is the way it came off.
    Input or ideas?
  2. john.schaefer77

    john.schaefer77 Well-Known Member

    You have it right. The weight goes towards the trans. I got an aftermarket flexplate that has that weight on the other side and makes it easier to find a converter.
  3. john.schaefer77

    john.schaefer77 Well-Known Member

  4. Bens99gtp

    Bens99gtp Well-Known Member

    These flex plates listed above don't fight our crankshaft right. At least the one I got for mine didn't.

    The converter shouldn't be tight against converter. There should be an 1/8th inch or so space between them when transfer is bolted to motor and converter is fully seated into the trans
  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Torque converters meant for Buick engine/transmissions have the converter mounting on pedestals to avoid contact with flex plate weights. Other manufacturers don't.


  6. Dr. Evil

    Dr. Evil Silver Level contributor

    Thanks for the reply. It was a bit tighter than 1/8th inch clearance when I bolted it up but, it went together.
    It actually moved today under it's own power so that was nice. Open exhaust though so nothing more than gentle moving around. Put a couple hours on it today dialing it in. I have too much stall and/or not enough gear. Probably going to drop down to a 2200-2400
  7. HotRodRivi

    HotRodRivi Tomahawks sighted overseas

    You no the torque converter expands a bit when hot. Also a stock flexplate is guarenteed to crack.

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