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Thread: 4L80E 3-4 Large Shift Time Error/TCC Cycling After Shift

  1. #11
    Joe (Moderator) joecar's Avatar
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    What is the pid SHSOLA (I'm out of town away from my laptops)...?

    The checkballs wearing into the separator plate are a concern... there are various wearproof balls/separators available (e.g. Sonnax).

  2. #12
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    Transgo too

  3. #13
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    Quote Originally Posted by joecar View Post
    What is the pid SHSOLA (I'm out of town away from my laptops)...?

    The checkballs wearing into the separator plate are a concern... there are various wearproof balls/separators available (e.g. Sonnax).
    New valve body, solenoids, and accumulator are already in the trans, but the separator plate is an interesting thought. There was what my inexperienced eye thought was a small amount of wear, but unfortunately it looks like I didn't take any pictures. That would be a cheap thing to try.

    SHSOLA is shift solenoid A. I was trying to match up the shift solenoid action vs. commanded shift vs. actual engine speed drop, and that all checked out.

    I did bump the shift pressure up for 3-4 pretty significantly just to see what it would do...it actually seems to show some kind of tie up happening where now it is pulling the turbine speed down too much before it eventually ends up where it should be. It also seems to be pulling engine speed down a bit, but that could also be torque reduction. Reported shift times are definitely quicker.

    I don't think there's an issue with the speed sensor because the only artifacts I can find in any of the datalogs are this 3-4 shift behavior.

    Below screenshot has accel and torque pulled out for visibility, but ~250 ft lbs and 35% steady throttle. Stock tune does not have any torque reduction on 3-4 shift. I added torque reduction in an effort to speed the shift up until I figure out what's wrong with the hardware.

    Click image for larger version. 

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  4. #14
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    https://transgo.com/

    They will like it that you can alter the computer.

    It's the plate.

  5. #15
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    Got a plate and gaskets on the way, we'll see where that gets me.

  6. #16
    Joe (Moderator) joecar's Avatar
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    TCC should be releasing during shifts.

    Log the pid GM.GEAR which is decoded from the solenoids A and B, it is easier to digest.

    Also log GM.TCCSTATE and GM.TFMPCS and GM.LASTSHIFT.

    Drop some pids to get the fastest logging rate (10 frames per second for LS1).

  7. #17
    Joe (Moderator) joecar's Avatar
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    Yes, TransGo also.

  8. #18
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    Have the plate, got new balls as well, forgot to order the separate accumulator gasket so waiting for that to show up. Have a road trip coming up, and decided I'm not going to risk causing other issues swapping everything out until I get back from that trip.

    I do have GM.GEAR in there, the solenoid A was just for that one log so I could see what that would show me, if anything.

    Logging rate is a good idea, I'll see if there's something that's getting aliased out of the data.

    GM.TCCSTATE shows "off due to slip" when the converter pops in and out of lockup. The slip number is actually negative, and checking engine speed vs. output speed, there isn't actually any slip occurring. It's only showing slip between turbine speed and output speed, somehow.

    I have TFMDC% in there, have no tried TFMPCS to see what that shows me.

    LASTSHIFT is in there, it's generally in the .25 to .4 range for 1-2 and 2-3 which is where it should be. target is .35 generally. For a "good" 3-4 shift, it's in the .7 range. 90% of the shifts with any torque behind them are 1.88 seconds. Always exactly 1.88, never more, never less.

    I would like the TCC to release during shifts, but I haven't changed anything in the tune that would make that behavior different than stock. It has stayed locked through shifts based on seat of the pants feel since the day that I bought it with an untouched tune. The only thing we have control over through software is "allow TCC to lock during shift" checkbox, but all this seems to do in my testing is allow simultaneous upshift+TCC lock instead of stock, where the shift has to complete before lockup can be commanded. This is turned off.

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