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What should I do next?

  • Buy a stage 3 Suncoast transmission

    Votes: 0 0.0%
  • Buy a six speed conversion from Dmax tuner - load up the parts cannon with a TCM and valve body

    Votes: 0 0.0%
  • Pull trans (again) and install full transmission seal kit

    Votes: 0 0.0%
  • Buy a five speed valve body

    Votes: 1 100.0%
  • Power brake it and listen to my turbo spool until it either moves or explodes

    Votes: 0 0.0%

  • Total voters
    1
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Discussion Starter #1 (Edited)
Hey all - first post here, hoping to tap some knowledge. For reference, I'm a GM dealer technician, so I have access to factory service information and scan tools.

My daily is a 2005 Silverado 2500, LLY, with about 150k on the clock. My turbo vanes stuck about nine months ago, and my injector balance rates took a dive about six months after that. A few weeks ago, I finished a relatively extensive list of modifications - details are listed in my sig. I've been running into issues with the transmission, and I'm thoroughly stumped, along with my shop foreman, tuner, and PPE.

My transmission build went smoothly. Made the valve body modifications folllowing PPE's instructions, and the clutches are a no brainer. Inspected pistons and seals along the way; no issues found. The clutches that came out were in excellent shape, and we found no significant debris or metal in the pan. Now, engine is running beautifully, but I have a strange transmission issue. Allowed the transmission fluid to warm up and set fluid level, then attempted fastlear using Tech2. No dice - no explanation or DTCs, but the scan tool sticks on the initial park calibration screen. Okay, maybe the increased line pressure is messing with it - I figured I'd go for a test drive and start the learn process manually. Selected reverse, truck shifted hard, but normal considering it hasn't been learned. Selected drive, got another hard shift, then took my foot off the brake. Truck creeped forward about three feet, then slammed into what felt like park - rear wheels locked up, truck skidded to a halt; no DTCs set, no MIL.

Grabbed the Tech2 again, and put the truck in drive. Commanded gears using the scan tool, and found the transmission only locking up in first and third gears. Commanding second, fourth, or fifth yields the correct gear ratio and normal creeping speed. Reverse still works normally. To me, this elimnates park pawl issues. Also, I'm discounting the toruqe converter because the engine idles smoothly while the trans is locked up. Pored over clutch apply charts, solenoid charts, and hydraulic circuits, and found nothing in common between first and third that wasn't also shared with other gears. Contacted PPE, and they claimed to have encountered this issue in the past. They told me the 4-5 clutch piston inner seal was leaking, and applying fluid pressure to both sides of the piston. This doesn't add up looking through SI, but hey, they made the kit, they must know better, right? Wrong. I replaced the lip seal they recommended, as well as the 1-2-3-4 piston inner seal - my dealership happened to have one in stock, and I figured it would eliminate telephone errors bewteen me, the customer service rep, and PPE's transmission guy. Rebuilt the C1/C2 housing with the new seals, reinstalled the trans this morning, and, shocker, no change. Same issue, and same results when commanding gears with Tech2.

My team leader is telling me it has to be "in the valve body," but he doesn't have any justification beyond "it has to be." My tuner and another local builder have no ideas, but they're both leaning towards a hydraulic or electrical concern as opposed to mechanical or software. I asked my tuner specifically whether or not this is an artifact of the tunes, perhaps interfering with the TCM's stored reference values, but he's steadfast - he wouldn't even know where to start trying to fix it with software. I'll be contacting PPE Monday morning once their customer service department reopens, of course, but I'll take all the advice I can get.

Yes, I should have bought a Suncoast prebuilt; penny wise pound foolish. I did everything all at once, please don't judge me.

So, I have a five speed Allison locking the rear wheels in first and third. Anyone run into anything like this before?
 

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I don’t see a way that you could have a clutch pack or apply issue. Toss that valve body to the side and put a untouched stock one on it. My money is that one of the valve body mods is screwing you
 
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