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6.2 flexplate differences.

Discussion in '1982-Present GM Diesel' started by colbystephens, Jan 27, 2006.

  1. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    so my machine shop called me a couple days ago saying that they were getting ready to balance my '83 6.2 engine and it turned out that my flexplate needed replacing. so i brought them another flexplate to check out off of an '82 6.2 engine. i just got a call from them and they said that it's not a match. apparently the holes in the flexplate for the bolts which hold it to the torque converter are not the same pattern. i found this very wierd b/c as far as i knew, it was easy to mix and match trannies and motors in pretty much any situation without changing flexplates. am i mistaken? what do you make of this?? thanks!
     
  2. Muddytazz

    Muddytazz 1 ton status

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    They are full of crap, they are the same.
     
  3. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    that's kind of what i was thinking, but they said that when laid ontop of one another, the bolt holes do not line up - one ring of holes having a smaller diameter than the other. maybe i should talk to them again.
     
  4. kennyw

    kennyw N9PHW Premium Member

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    There are two patterns in every flex plate with 6 bolt holes for the torque converter... tell them to rotate it to the next set of bolt holes and it should line up then. The 700R4/TH350 uses the smaller pattern of 3 holes for gas motors and the TH400 uses the larger pattern of 3 on gas motors... on the diesels though I'm not sure if all 6 are on the same bolt circle or if there are 2 different flexplates for the 700R4 vs TH400.
     
  5. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    interestingly, this second flexplate is off of that 6.2 you sold to my buddy thru troy, kenny.
     
  6. kennyw

    kennyw N9PHW Premium Member

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    k... think that one was a TH400. But there wasn't a tranny in the truck when I got it.
     
  7. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    well, mine's got a 350 - so idk.
     
  8. kennyw

    kennyw N9PHW Premium Member

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    If you hold the 2 flex plates up together and the bolt pattern doesn't match you would only need to rotate one of them 60 degrees to the next hole (360/6). If they both have the dual pattern in them, they will now line up.
     
  9. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    for what it's worth, i picked up my motor today and sure enough the machinist was correct. the two flexplates have a different pattern for the torque converter. were a circle to be drawn connecting all of the clearance holes together through their centers, the diameter from the center of one clearance hole to another was slightly larger than on the other flexplate. :dunno:
     
  10. kennyw

    kennyw N9PHW Premium Member

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    My guess is 700R4 and TH400 use different flexplates on the 6.2L
     

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