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    Results 1 to 5 of 5
    1. #1
      Join Date
      Dec 2014
      Location
      Great Falls, Montana
      Posts
      134
      Country Flag: United States

      Speedometer help.

      Having issues with my speedometer. The car is a 71 Formula 455 and a new speedo from classic industries. I am running a T56 with a Cable X box to drive the factory speedometer. I have the box set to the proper settings for my tone ring. I took the car for a test drive to compare it to gps. The odometer is just about dead on. The issue comes from the speedometer part. When I'm hitting about 35-37mph as indicated by gps; the speedo reads about 20mph. I'm thinking there's an issue with the speedo, but I am not sure considering the odometer reads correctly. Any thoughts or suggestions will be greatly appreciated.


      1971 Firebird Formula 455HO 6 speed
      2017 GMC Sierra Denali Ultimate Pearl White 6.2L
      2013 GMC Sierra 5.3 6 Speed Pearl White, SLP 1.9L Supercharger(Sold)


    2. #2
      Join Date
      Apr 2001
      Location
      The City of Fountains
      Posts
      15,375
      Country Flag: United States
      If the odometer is spot on, how can the speedometer be off?

      Andrew
      1970 GTO Version 2.0
      1967 Cougar build
      GM High-Tech Performance feature
      My YouTube Channel Please Subscribe!
      Instagram @projectgattago
      Dr. EFI
      I deliver what EFI promises.
      Remote Holley EFI tuning.
      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

    3. #3
      Join Date
      Dec 2014
      Location
      Great Falls, Montana
      Posts
      134
      Country Flag: United States
      Tell me about it. Confuses me.

      1971 Firebird Formula 455HO 6 speed
      2017 GMC Sierra Denali Ultimate Pearl White 6.2L
      2013 GMC Sierra 5.3 6 Speed Pearl White, SLP 1.9L Supercharger(Sold)

    4. #4
      Join Date
      Aug 2004
      Location
      Jacksonville, FL
      Posts
      1,539
      Country Flag: United States
      Which T56 do you have and what reductor wheel setting are you using?
      Chris
      1968 Chevy Camaro SS
      LS3/T56 Ridetech suspension


    5. #5
      Join Date
      Dec 2014
      Location
      Great Falls, Montana
      Posts
      134
      Country Flag: United States
      Running an lt1 t56 with all the viper upgrades. Tone ring is the viper 10 tooth. The cable x box is set right as the odometer is reading right.

      1971 Firebird Formula 455HO 6 speed
      2017 GMC Sierra Denali Ultimate Pearl White 6.2L
      2013 GMC Sierra 5.3 6 Speed Pearl White, SLP 1.9L Supercharger(Sold)