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Thread: Incorrect 4L80E Shift Points

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    Default Incorrect 4L80E Shift Points

    Hello. Details of what I'm working with. Using a Holley Terminator LS MPFI system (Dominator ECU). Engine 6.0 liter LQ9. Transmission is a 1996 4L80E with a turbine sensor and VSS sensor. I've ensured the connectors are correctly installed on their proper sensors, VSS being the aft sensor.

    What's going on is the speed signal I see on the handheld while driving is low by about 20% across the range. Tire size is 37", gears are 4.86 and those parameters have been correctly inputted into the EFI software. I'd like to know why it's not accurate and what I could do to fix it.

    Also have a situation where around 25 MPH actual road speed it'll shift from 2nd to 3rd and if I don't apply more throttle and accelerate to 30 MPH, or above, the ECU will apply the clutches and release them, over and over till I either downshift manually or accelerate to a speed above 30 MPH. Odd behavior, not sure if related to the overall low speed signal.

    Main question is, how do I get the speed signal accurate that I see on the handheld? Just play around with tire size and gear ratio till it's correct? I figured it should just be correct since that's what is physically on the rig. I just feel like there's something I'm missing, so I'm asking for advice.
    Last edited by JeepCJ-6; 04-22-2019 at 11:36 AM. Reason: Spelling Error

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