Transmission just gave out - GV shifting too hard?

Discussion in 'Transmission & Driveline Topics' started by ULTM8Z, Sep 22, 2019.

  1. jakeshoe

    jakeshoe Veteran Member Lifetime Gold Member

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    Hughes makes a good converter.

    The GM2500 converter will be a stock core 12" diameter converter with the impeller fins bent slightly negative to yield the higher stall speed.

    A 258mm (10.25") core could be built to yield a similar stall speed, less slippage driving away from a dead stop, and more efficient all around.

    The deep 1st gear ratio of the 700 will make a converter slip less anyway in that situation.

    A custom built converter will yield better driveability.
     
  2. ULTM8Z

    ULTM8Z Veteran Member

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    Thanks Jake.

    Looks like the input drum broke. He thinks if the converter failed it could have resulted in collateral damage to the input drum.

    If that's the case it makes it an even bigger "DOH!" that I reused the same old converter on the last rebuild to save some money... :confused:
     
    Last edited: Oct 2, 2019
  3. 77 cruiser

    77 cruiser Veteran Member

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    Jake's Performance makes a good converter too.:cool:
     
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  4. jakeshoe

    jakeshoe Veteran Member Lifetime Gold Member

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    As I stated before. I highly doubt the converter broke.
    Two things fail in a converter that cause a total loss of drive. Turbine hub weld when an aftermarket converter with a different hub welded in fails. This isn't what you have anyway using a stock core.
    And it's a rare freak failure.

    Or the stator comes apart and completely trashes the inside of the converter. This usually results in some movement for awhile with a bad noises and generates a ton of metal.

    Doesn't sound like either of your scenarios.

    Not only that, you're not making enough power to kill a stock 12" stator.
     
  5. ULTM8Z

    ULTM8Z Veteran Member

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    Jake, do you think the hard shift could have contributed to it? He didnt think so....

    He also said it was rare to see these things fail...
     
  6. jakeshoe

    jakeshoe Veteran Member Lifetime Gold Member

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    700s are notorious for breaking. Transmission shops are still making a living on that design.

    Hard shifts probably contributed. It was working OK and then seems to have killed a hard part almost immediately after GV install.

    I've warned about the shifts of the GV being "unrefined".

    A transmission has variable pressure and an accsimulator circuit that varies shift feel based on load. Gear Vendors doesn't.
     
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  7. ULTM8Z

    ULTM8Z Veteran Member

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    I guess we'll see what happens.

    I'll see how it is with the looser converter too. The only shift that seems like it would qualify as "too hard" is the 1st to 1st-over. Like I said, the others feel like 60-70% softer (pretty much like a typical shift kit). So if those get even better with the new converter, then I'm that much farther ahead.

    So worst case I suppose is no hard throttle upshifts on the 1st to 1st-over.

    Not a big deal... I'm not racing the thing and there are so many more benefits than just that one shift that the GV is still worth every penny IMO... especially if later I go a 3.90 axle ratio with the benefit of a effective double OD.
     
  8. jakeshoe

    jakeshoe Veteran Member Lifetime Gold Member

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    Build the transmission to handle the power.
     
  9. 80sz

    80sz Veteran Member

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    I have had a 700 with a 406 small block. I broke it, 2x. 450hp but did do some 150 nos runs on it also. When I swapped back to a turbo 350 I realize how deep that first gear is, the 3.06 is a stump puller. Now that you have the overdrive the 350 might be a better choice? Mabe go nuts and get a 10” 3500 stall and get crazy? It’s not going to slip and rev all over the place. I easily lumped along a 1500 rpm in third gear with 3500/10”. A good converter will flash to rpm but hold also at low rpm.
     
  10. C4Racer

    C4Racer Veteran Member

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    a looser converter will also soften the effect of the hard GV shift.
     

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