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Thread: 2003 TRAILBLAZER LT, 4.2, 4L60E. hard 1-2 shift

  1. #1
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    2003 TRAILBLAZER LT, 4.2, 4L60E. hard 1-2 shift

    what can i change to lessen the hard 1-2 shift on this transmission. this is the only issue i have with transmission. i just got mpvi3 yesterday so this is all new to me. thanks for any info. attached is the current tune, i believe stock
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  2. #2
    Senior Tuner TheMechanic's Avatar
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    First things first. Before you go messing with a stock tune, does it have a transmission, TAC, or any other codes in the PCM? If so diag those first before messing with the tune. Those do not typically have a harsh shift when everything is bone stock.

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    0 codes and i forgot to mention po said they put in a corvette servo.

  4. #4
    Senior Tuner TheMechanic's Avatar
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    That servo will firm up the shifts.
    Shifts are pretty subjective. Do you have a stock vehicle to compare to? You could soften it up with some adjustments.

  5. #5
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    I don't like to undo shift firmness from shift kit type parts like that.

    I'd go back to the OEM servo to get the shift you want.
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  6. #6
    Senior Tuner TheMechanic's Avatar
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    Quote Originally Posted by Alvin View Post
    I don't like to undo shift firmness from shift kit type parts like that.

    I'd go back to the OEM servo to get the shift you want.
    Totally agree. I tell customers no problem on aftermarket clutches, zip kits, etc etc but no mechanical shift kits given the ability to put the shift kit in electronically in a far safer better manner.

  7. #7
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    GM Gen4 Injectors v2.1.xls
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  8. #8
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    Thank you. I’ll try this weekend

  9. #9
    Tuning Addict blindsquirrel's Avatar
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    The 70E servo might be a better choice. (combined with adding some TM at the 1-2)

    https://www.sonnax.com/tech_resource...for-the-4l60-e
    GM Gen4 Injectors v2.1.xls
    "My life has become a single, ongoing revelation that I haven't been cynical enough."
    Funny how accounts marked as 'banned' are still able to log in and do stuff on the site, huh?