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Remanufactured DRAC/VSSB Modules (& Custom Calibration)

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DRAC is Digital Ratio Adapter Controller (TBI DRAC, GM DRAC, Buffer Module)
VSSB is Vehicle Speed Sensor Buffer (TBI VSSB, GM VSSB, Speedometer Buffer)

DRAC/VSSB Module Year/Make/Model Applications

DRAC and VSSB modules are primarily applicable 1989-1995 TBI Gas and 1990-2002 Diesel applications.


  • 1992-1995 Chevy GMC Truck C/K 1500, 2500, 3500, 3500HD TBI gas (6,8 cylinders)
  • 1992-1995 Chevy GMC Blazer, Tahoe, Yukon TBI gas (8 cylinders)
  • 1992-1995 Chevy GMC Suburban C/K 1500, 2500 TBI gas (8 cylinders)
  • 1990-1995 Chevy Van G10, G20, G30 TBI gas (6,8 cylinders)
  • 1990-1995 GMC Van 1500, 2500, 3500 TBI gas (6,8 cylinders)
  • 1989-1995 Chevy Astro Van TBI gas (6 cylinders)
  • 1989-1995 GMC Safari Van TBI gas (6 cylinders)
  • 1991-1995 Chevy CMC P30 TBI gas (6, 8 cylinders)
  • 1989-1995 Chevy GMC S10 & Sonoma Pickups TBI gas (4,6 cylinders)
  • 1989-1995 Chevy GMC S10 Blazer, S/T15 Jimmy TBI gas (4,6 cylinders)

  • Diesel

  • 1992-2000 Chevy GMC Truck C/K 1500, 2500, 3500 6.5L Turbo Diesel
  • 1992-2002 Chevy GMC Truck C 3500HD 6.5L Turbo Diesel
  • 1994-1999 Chevy GMC Blazer, Tahoe, Yukon 6.5L Turbo Diesel
  • 1990-1999 Chevy GMC Suburban C/K 1500, 2500 6.5L Turbo Diesel
  • 1990-1995 Chevy Van G10, G20, G30 6.5 Diesel
  • 1990-1995 GMC Van 1500, 2500, 3500 6.5 Diesel
  • 1996-2002 Chevy Express G10, G20, G30 6.5L Turbo Diesel
  • 1996-2002 GMC Savana 1500, 2500, 3500 6.5L Turbo Diesel
  • 1991-1999 Chevy CMC P30 (6.2L D, 6.5L D, 6.5L Turbo Diesel)
  • 1999-2005 Workhorse P30 P42 6.5L Diesel
  • 1994-1995 Hummer H1 6.5L Diesel - OE Cal Only
  • 1996-2004 Hummer H1 6.5L Turbo Diesel - OE Cal Only

  • Note: All applications for this style of module are not covered, please consult with us prior to purchase if you're unsure of your application. We will need your application, the 3 or 4 digit Broadcast code as well as GM Part number off your current module to verify this is what you need.

    Failed DRAC/VSSB Modules Symptoms in OEM Applications

    Replacements for failed OE Module are readily available and in stock from UD Module. DRAC and VSSB Modules fail in several ways and contribute to other systems malfunctioning on the vehicle. We offer working solutions to OE application modules due to these modules no longer being supported or available from GM over the counter for most applications. Finding the correct direct replacement module is very difficult in the used market, say at the salvage yard or online and you don't know what you're getting. Rely upon UD Module for the known-good tested and verified solution.

    Common Symptoms of DRAC VSSB Failure:

  • ODB-I Fault code for VSS
  • ODB-II Fault code for VSS
  • Inoperative Speedometer (stays at zero)
  • Unresponsive speedometer (sits at zero then jumps to 15)
  • Jumpy Speedometer
  • Inoperative Cruise Control
  • ABS Brake System Faults
  • Transmission shifting problems 4L60E
  • Transmission shifting problems 4L80E

  • DRAC VSSB Module Products

    Original Equipment (OE) DRAC VSSB Replacement

    Select this module for a direct OEM replacement module that is calibrated based on the Broadcast Code and GM Part Number from your old module. This is intended to be a replacement module to replace your failed factory module.

    Please be prepared that We Require both the broadcast code (big letters) and the part number (number under big letters) for an order, but can do on either. So you'll need to have the info off the old module (typically removed).

    Custom DRAC VSSB Based on Gear Ratio & Tire Size

    Select this module for speedometer calibration when tire size and or rear end gear ratios have changed from factory. We can calibrate for gear ratio or tire size combinations with great granularity with factory quality.

    In preparation for ordering We need to know your gear ratio and tire size, additionally we will need to know the what module you have now (remove it) to provide broadcast code (big letters) and part number (number under big letters).

    Do It Yourself (DIY) Dip Switch DRAC VSSB

    Select this module for a user-calibrateable module equipped with DIP Switches. This is for when you want calibrate the module yourself and make changes later for your own custom application.

    This module undergoes the same testing and verification as our other service modules. Calibration is based on your own math and calculations for your gear ratio and tire size. This module carries no support.

    DRAC VSSB "Tech Support" Service for UD Module units

    Paid technical Services for troubleshooting DRAC and VSSB modules purchased from UD Module are available. Service is in the form of email guidance through explanation of how the system works, wiring diagrams, pin outs, and test procedures for the module and various systems it operates tailored to your exact vehicle application.

    Includes up to 20 email responses and is based on a per incident per purchase limitation that is effective for 30-Days after purchase. Must own or purchase from us a Digital Multi-meter for test procedures.

    DRAC VSSB Adaptation and Consultation Service

    Paid consulting services for wiring and adaptation expertise. Examples include driving aftermarket speedometers off DRAC and VSSB modules, and instrument cluster conversions and transmission conversions.

    Flat rate default service offering, whereby you can ask technical questions saving hours and days of your own research. This service is relied upon when one of these units is being used in a non-original application state. Excludes UD Module proprietary information.

    DRAC VSSB Parts - Pigtails and Wiring products

    Parts related to DRAC and VSSB Modules in OEM repair usage and adaptations. Pigtails for the DRAC and VSSB module connection, and twisted pair wire for module to VSS replacement.

    Pigtails from used clippings to new connections for repair, Vehicle Speed Sensor (VSS) pigtails for various known OE sender applications.

    DRAC VSSB Parts - Mounting Brackets and Fasteners

    Mounting parts for DRAC and VSSB Modules in OEM repair usage and adaptations. OE mounting brackets for mounting modules and fastners used with mounting DRAC and VSSB module enclosures.