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Thread: P0730 Incorrect Gear Ratio Code

  1. #1

    P0730 Incorrect Gear Ratio Code

    I am trying to figure out this code. Had this before on my old 3800SC setup on my 88 Fiero. Well I now have another 88 Fiero with a 3800SC with the 4t65eHD transmission. Transmission code is 2FCB. Which is a 02 Park Avenue Ultra Transmission with 3.29 Differential. The drive sprocket should be 37/33 which is 1.121 in the HP tuner program itself when looking at the tables. The gear ratio in that tab is 3.29 which manual adjusts the speedo, etc for this and gives it the 2.93 final drive. Now my question is the Engine and Transmission is a 02 Buick Park Avenue Ultra and looks like the PCM is a 2000 Buick LeSabre Custom which is a NA 3800. The previous tuner flashed a SC bin file I believe and I am not sure what would be causing the gear ratio error. The calculated gear ratio in 3rd is 0.891 and should be 1.00. I have tried a few different setups. It was originally 3.29 with a 1.00 drive sprocket. I then tried a 3.29 with a 1.121 drive sprocket which should be correct. I don't know what else to try? Doing 2.93 with a 1.00 drive sprocket. The manual shift tables when I input anything other than the 3.29 with a 1.121 sprocket should calculate the right shift mph. With the 3rd gear calculated ratio being 0.891 as both setups in HP Tuners when scanning, what should the setup be to make it 1:1?

    Any help would be appreciated on this.

  2. #2
    Potential Tuner
    Join Date
    Sep 2015

    Re gear ratio

    Did you figure this out yet? Guy just brought me an 04 impala, they have swapped the engine and trans from another car, trans has a different final drive ratio. I see some options in the speedo settings in the tune, but I'm reluctant to pull the trigger on the credits just yet.