Results 1 to 5 of 5

Thread: gear ratio and tire size change

  1. #1
    Potential Tuner
    Join Date
    Feb 2020
    Posts
    3

    gear ratio and tire size change

    some background: I am building a 96 gmc sierra into somewhat of an overlanding truck/fun camping vehicle, and two changes I am planning on making are the axle ratio (3.42 -> 4.10) and the tire size (~29 inch to 33).

    From what I can see, I shouldn't need to change anything with regards to the front ABS wheel speed sensors, because all 4 tires are changing size, but because I'm changing gear ratio, the rear wheel ABS signal (which uses the VSS sensor output from the PCM) will need to change.

    My question is, before I drop $500 on buying/retrofitting a 411 PCM to use HPTuners, and buying HPTuners, does anyone know if the VSS output to the ABS module changes when you change gear ratio in the PCM? Am I just wrong in my assumptions about the ABS system/signals?

    Another note, I will not just be tearing out my ABS (even though it isn't the greatest system). From my understanding, Canadian law requires safety systems that came on the vehicle to be installed and working. Also, I'm sure my insurance would have a conniption. Please feel free to correct me if I am wrong.

    Thank you for your help.

  2. #2
    Senior Tuner mbray01's Avatar
    Join Date
    Dec 2013
    Location
    Slidell, La.
    Posts
    1,015
    There is an abs specific output, that you can change while monitoring abs wheel speed vs trans output wheel speed.
    Michael Bray
    Rusty Knuckle Garage
    Slidell, Louisiana
    20yr Master Tech.
    Advanced Level Specialist
    Custom Car Fabrication, Customization, High Performance.
    GM World Class Technician
    Shop Owner

  3. #3
    Potential Tuner
    Join Date
    Feb 2020
    Posts
    3
    So I understand what you are saying: There is a place in the HPTuners software that I can use to change the rear channel ABS output from the PCM to the ABS module? If so, then that is awesome, and thank you!

  4. #4

  5. #5
    Senior Tuner mbray01's Avatar
    Join Date
    Dec 2013
    Location
    Slidell, La.
    Posts
    1,015
    yep
    Michael Bray
    Rusty Knuckle Garage
    Slidell, Louisiana
    20yr Master Tech.
    Advanced Level Specialist
    Custom Car Fabrication, Customization, High Performance.
    GM World Class Technician
    Shop Owner