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Thread: Burning transmissions like marshmallows at a campfire

  1. #1
    Junior Member
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    Apr 2007
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    Default Burning transmissions like marshmallows at a campfire

    Vehicle- 2005 GMC Sierra 2500HD 6.0 4L80 with LSA heads, LSA supercharger, pulley, 21x/22x cam, efans, injectors, pump, etc. 4.88 gears with 35” tires and lockers. The tune is COS5, with a segment swap running e85/ Flex Fuel in Speed Density.

    Short story- Does anything stand out in my tune that would be responsible for repeat transmission failure? I’m thinking at this point that I screwed up somewhere along the line.

    Extra Long Story- I personally rebuilt the trans in the truck 6 year ago. It lasted for 5 years with good parts and an HD2 kit. When it burned up last year, I rebuilt it again but did away with the HD2 in favor of an internal dual feed mod. It was at this time I also sought to correct the exceptionally hard shifts I endured for the prior 5 years. I found the culprit to be the max pressure fault enablers for the failed MAF. After getting things together, the trans worked well for about a week and had good pressure during this time, and then lost holding in reverse. I pulled it, got a new core so there was no commonality of parts, and took it to a local builder. He installed an HD2, went through the pump and valve body with a fine tooth comb, built the trans, and said I should be good. Again, the trans lasted about a week, but this one didn’t lose reverse, it smoked when laying the hammer down and I lost third and fourth and perhaps more. I paid good money to have it rebuilt, and I know the builder will warrant it, but if this is my error, I don’t want to make it his responsibility, and I also want to resolve the issue and not go through this again. I’m about ready to put the thing back to stock and sell the truck. It was great for the five years after the first trans build, sans the hard shifts. Are my pressures too low? Is there something happening with the pressures and scaling due to the segment swap that was band aided by the max pressure enabler?

    Thanks for the help!
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    Last edited by smokeysbandit; March 3rd, 2023 at 05:25 AM.

  2. #2
    Lifetime Member
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    Default

    Do you have a pressure gauge to monitor pressures with?

  3. #3
    Junior Member
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    Apr 2007
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    Default

    I do, and pressures were good at install, but perhaps I was hitting conditions that were not monitored at the time. That's why I'm looking for tune feedback.

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