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Custom Calibrated DRAC Module VSSB Module TBI Gas & Diesel


The speedometer calibration comes from physically reprogramming the DRAC or VSSB Module to replace in your vehicle. Whenever you change to a different (taller or shorter) tire or gear ratio on your truck the speedometer will be off. We can calibrate the speedometer back to the calibration that the factory sets on the these speedometers and more. Any possible gear and tire combination is supported with great granularity.

Why would you want to calibrate your speedometer?

  • Have an accuate measurement of vehicle speed.
  • Resolve a lagging speedometer.
  • Measure actual mileage onto vehicle
  • Calculate fuel mileage from odometer or trip-odometer.
  • Correct ABS (Anti-Lock Brake System) operation.
  • Correct cruise control operation.
  • Transmission shift timing and quality characteristics.
  • The DRAC/VSSB Module afffects all these and more!


  • You can order directly below. Also, helpful information is below the form to help with the order if needed.

    Custom Calibration DRAC VSSB Based on Gear Ratio & Tire Size
    This module is calibrated based on gear ratio and tire size. This calibration will get you a factory quality calibration with GM type gear ratios as well as aftermarket gear ratio combinations. Got a Ford rear differential gear in your GM with a different ratio than commonly available? No Problem! We can calibrate for any gear ratio or tire size.

    Please fill the form to the right out to the best of your abilities. We need to know your gear ratio and tire size and the type of DRAC module your vehicle or configuration needs. DRAC type can be determined best by it's part number and broadcast code. We can also determine the type by the application (Year, Model, Series, Engine).

  • $10 Core Charge (shows as Handling) applies

  • DRAC Type Setting Quality $119
    Year, Model, Series, Engine
    1995 Suburban K2500 6.5 Diesel
    Tire Size Gear Ratio
    245 75 R16 4.10
    Broadcast Code, GM Part Number
    PYT, 16185145


    This module will be shipped out next day via USPS Priority Mail.

    USPS Express Mail & International Priority Mail available at checkout.



    How do I provide the information needed for an order?

    UD Module remanufactures the various DRAC/VSSB modules and then creates the exact calibrated module you need for replacement. For custom calibrated modules where a differential gear ratio or tire size has changed we need the current Gear Ratio and Tire Size. To match the correct module for replacement we need you to remove your original module and record the Broadcast code (typically 3-big-characters) and/or the GM Part Number (under the 3-character code) and we build you a correct matching replacement module. Read below for more details on information needed.

    Gear Ratio

    To find your vehicle's Rear End (differential) gear ratio, the RPO codes list in your glove box is the easiest way. This is the sticker inside the box with a lot of 3-character codes. Find the gear code, this is typically GU4 (3.08) GU6 (3.42) GT4 (3.73) and GT5 (4.10) being the most common. Another method, you can call a GM Dealer's service department and provide them with the last-eight digits of your VIN and they can tell you the factory build gear ratio.

    Tire Size

    Check the current tire size on the vehice. The absolutely preferred tire size measurement will be to use the P-Metric size on the sidewall. For example: 245/75 R16, please do not provide an estimated tire size diameter when a P-Metric or true size (like 33x12.5 R15) is available as this greatly affects accuracy of calibration.

    Broadcast Code and Part Number


    First, the module will likely need to removed from the vehicle to retrieve the information. You'll need the broadcast code and the GM Part number off the old module for the order form above.

    Broadcast Code   In Blue

    Part Number   In Green



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