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Thread: How about a transmission tuning tutorial!

  1. #1

    Default How about a transmission tuning tutorial!

    I would definately like to know more about dialing in the automatic transmissions for performance improvements. Items like firming up shifts, changing shift rpms, etc....

    There seems to be quite a few parameters for the transmission yet some are not ones that tyically need to be touched. I am still a bit unsure of the best way to firm up the shifts as well as properly adjust shift points. Seems like a sticky or a tutorial would be kind of nice.

    Any thoughts??

    Last edited by Redline Motorsports; January 29th, 2006 at 07:47 AM.


    2006 ZO6 895/866 with APS TT
    2010 SSRS Camaro HTR-900TT (798/801)
    2011 HTR-850R Camaro
    2012 ZL1 Auto (10.33@135 MPH) Video Here!

  2. #2
    Senior Member
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    Aug 2005


    I agree, I would really like some more info on this as well.
    1992 Turbo LSX Notchback Mustang 275 radial car - under construction
    2008 Sierra 2500HD Duramax

  3. #3
    Senior Member Wasted Income's Avatar
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    Dec 2005


    Yup, I agree
    2005 Silverado Duramax LLY - EFI Live Tuned
    1969 Chevrolet C-10 Pickup - Turbocharged 5.3L/4L80E - EFI Live Tuned
    1975 Avenger Jet Boat - 6.0L/Berkley pump - EFI Live tune in progress

  4. #4
    Joe (Moderator) joecar's Avatar
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    Apr 2003


    I don't have a tutorial written, but some basic steps that could be included for daily driver usage (feel free to add, delete, modify, correct, increase knowledge):

    a. Increase shift pressures 5-10%.
    b. Decrease shift times to aorund 0.3s.
    c. Decrease torque reduction at each shift by 5-10%.
    d. Adjust the upshift and downshift curves, BUT always keep the upshift curve higher than the downshift curve (i.e. at each TPS value, keep the upshift speed greater than the downshift speed); "hysteresis" prevents gear hunting.

    Go for a drive, logging various trans pids
    (vss, rpm, tps, map/maf, torque, tft, pcs, gear, shift times, shift errors, various tstates).

    Check "feel" of each shift (harsh, firm, soft, sloppy); harsh or sloppy is no good;
    if it's too firm:
    if line pressure pid shows high pressure at lower throttle positions, then reduce pressure for that shift, otherwise increase torque reduction;
    if it's too soft:
    if line pressure pid shows low pressure at higher throttle positions, then increase pressure for that shift, otherwise decrease torque reduction;
    If you break tire traction, how severe is it (little chirp at medium throttle is okay, big spin loose is not okay)...?
    You want firm positive shift, not harsh super firm jerking shift.
    Torque reduction curves have a big effect on shift feel.

    Are shifts occurring in the specified shift times...?
    Compare this with time taken for shift initiation to rpm drop; does it match...?
    If shifts are slower, then pressure may be too low (or trans worn out);
    If shifts are faster, then pressure may be too high;
    PCM may try to adapt by altering pressure;
    if pressure goes too low, clutches/band slip and burn;
    if pressure goes too high, pump wears out prematurely;
    You want shifts to be fairly reasonably quick, not overly quick, and not long drawn out.

    Does it shift too early or too late...?
    if too early, increase shift MPH;
    if too late decrease shift MPH;
    you may like it to hold longer thru each gear (reduces fuel economy, increase gearset wear);
    you may like it to sequence thru gears quickly (increases fuel economy, reduce gearset wear);

    Is WOT shift at the RPM you want...?
    Adjust WOT RPM and test it out;
    it may shift at a higher RPM, so watch out that it doesn't hit rev limiter.
    Note: WOT shift occurs as soon as both WOT MPH and WOT RPM are met.

    The ideas behind all of this:
    1. slow sloppy shifts allow clutches and band to slip during the shift, causing wear and heat.
    2. quick harsh hard shifts fatigue the hard parts, the driveline, the axle, and wears the tires and engine mounts.
    3. high line pressure wears the pump prematurely;
    4. excessive line pressure may damage the accumulator pistons and clutch/band servo pistons (and may blow the snap rings out of the ends of the cluctch packs), and may crack the case.
    5. quick firm shifts reduce the amount of time the clutch/band slips during the shift
    (the releasing component ramps down (slips during this), the applying component ramps up (slips during this);
    reducing the time taken for this reduces slip which in turn reduces heat and wear).
    6. overheated atf causes friction material to go bad and o-rings to go hard (and leak),
    and overheated atf loses its properties/qualities.
    7. nice quick crisp shifts make the car feel like a "performance" car;
    the conservative factory feel makes the car feel like a slow lumbering land yacht, and wears clutches/bands earlier; although in recent years the factory increased line pressure slightly and uses torque reduction to make the shift sloppy (which protects entire drivetrain).

    As with anything good (or bad), don't overdo it; don't overdo it; don't overdo it.

    Drag racing requires different characteristics, a stall converter, a shift kit, some reinforced hard parts, a bigger axle, bigger U-joints; of course, everyone already knows this.

    If you drag race and/or run a stall converter, it is a really good idea to install an atf cooler.

    Edit: Do not alter the PCS table; this table tells the PCM what pressures the PCS produces as a function of current and temp.
    If for some reason you adjusted the screw in the back of the PCS, you will need to adjust this table, but this is difficult.
    It's best not to alter either the PCS table nor the PCS screw, unless there's a very good reason.
    Last edited by joecar; January 21st, 2010 at 09:40 PM. Reason: Typos and formatting

  5. #5
    Joe (Moderator) joecar's Avatar
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    Apr 2003


    Too bad there are no tuning parameters for TCC ramp up/down.

  6. #6
    Lifetime Member
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    Oct 2003


    Nice post, joecar. Thanks!


  7. #7


    Wow! Great start!

    Maybe if we get enough input we can put together a step by step tutorial.

    We definately should set it up by level of tranny tuning needed. This could be a Level one tune for a slight firmer shift and raise the shift points to a real aggressive Level Three that could be for a high hp auto.

    Kind of the same way when tuning a bone stock car vs. a head/cam car. Some parameters in the bone stock tuning process as not even touched as they would be in the more aggressive setups.



    2006 ZO6 895/866 with APS TT
    2010 SSRS Camaro HTR-900TT (798/801)
    2011 HTR-850R Camaro
    2012 ZL1 Auto (10.33@135 MPH) Video Here!

  8. #8
    Joe (Moderator) joecar's Avatar
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    Apr 2003


    Good ideas.
    We need to organize it and tidy it up and think up all angles.

    Edit: I added 2 edits to the above description.
    Last edited by joecar; January 12th, 2006 at 08:53 PM.

  9. #9
    Lifetime Member
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    Jul 2005


    Dont get to many auto cars but so far I find the g/box kicks down to easily in normal mode so I have changed the tps kick down points while leaving the rpm points alone.
    In performance mode I change the upshift rpm's so the car revs closer to the limiter makes a big difference as the motor stays on the boil better.
    Reduced torque reduction by 50% I would'nt change it that much at sea level.
    Still dont get tyre chirp so some more experimenting is in order. Will have to wait for another auto car.
    \"You Can Never Have Enough Horsepower\"

  10. #10
    Forum tyhee Site Admin GMPX's Avatar
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    Apr 2003


    Quote Originally Posted by joecar
    Too bad there are no tuning parameters for TCC ramp up/down.
    Oh, no more requests please .
    Your post was a good read, there, tutorial is done.


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