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Thread: 2015 Tahoe change rear gear ratio

  1. #11
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    Got the Tahoe back. It still has the Reduced Power thing when you start it, but power is not reduced. I'll try backing the speed limiter down to 255 sometime today and see if it's still an issue.

    The new gears feel great. It still feels like I'm driving a big box, but the box isn't as big as it was.

    And now, for the important bit - the procedure for updating the shifting profile for a gear change works perfectly. This should work for tire size changes too. Aside from the shift speeds being lower, the Tahoe's shifting pattern feels identical to before the gear swap. If you moderator types want to copy it to a fresh thread and make it a sticky, be my guest.

  2. #12
    Joe (Moderator) joecar's Avatar
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    I can't see why it is throwing a REP DTC...

  3. #13
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    Thanks for looking into it. I've not had a chance to make any changes yet and it's nighttime here. I'll try to get something with it tomorrow and will report back. Going to try putting in 255/254, like the older computers had as a limit and see what that does. With the new gearing it's best theoretical speed is 207MPH but there's no way a stock 5.3L will drive that huge box that fast. I'll report back the results after.

  4. #14
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    OK, the error is gone. I went to the engine calibration, Speedometer, Speed Limiters, Parameters, and set H0129 to 240, H0157 to 239, H0158 to 239, H0161 to 238, and H0131 to 239. No other changes made.

    I suppose someone could sit down and load ever higher speeds in these fields until the error returns and possibly identify the cause from there, but as for me the error is gone and the speed limiter is set higher than the vehicle's actual top speed so I'm happy with it as it is. It's not like it'll ever go 200+MPH anyway.

  5. #15
    Joe (Moderator) joecar's Avatar
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    I don't understand why... but good job

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