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Thread: 6F35 2-3 shift tuning

  1. #1
    Tuner in Training
    Join Date
    Jul 2022

    6F35 2-3 shift tuning


    I already mentioned about my case on other threads, but decided to create a dedicated thread for this.

    I have a Fusion Titanium 2.0 Ecoboost AWD 2013 with 6F35 trans which have a very annoying shift delay (shift lag) specifically from 2nd to 3rd, which happens specifically on high engine load and when the trans is cold. Its not a flare, the trans does not slips during the 2-3 shift... it just "holds" the acceleration until the shift is completed.

    I monitored the SHFT_LAG PID on this specific gear change scenario (2-3, mid/high engine load) and i see values up to 1800ms when the trans is cold (fluid between 25 and 50 celsius), while on other gear changes i see it between 500 and 800ms).

    After the trans is warm (running for about 30 to 40 min, where the fluid reaches around 90 celsius), this lag reduces to around 900ms. On light engine load situation, independently if the trans is cold or warm, the shift lag measured by the PCM stays around 500ms.

    I already replaced the whole valve body (solenoid body + main control) and it didnt change. So, I checked the control signals of solenoids SSA/B/C/D comparing both scenarions and observed that, on high-lag situation, the command of SSB/C (both turn off from 2nd to 3rd) occurs is a much slower ramp (around 2000ms to complete) compared to the low-lag situation where the command of SSB/C takes only 1000ms to go from ON to OFF (ramp). See picture below showing the control signals of solenoids B and C when transmission fluid is cold (25?C) vs hot (90?C) captured with a simple OBD scanner on similar throttle and RPM cenario:

    2-3 shift Cold vs Warm.png

    The strangest thing is that the 2-3 shift is the only shift that presents an excessive time (SHIFT_LAG PID indicates around 2000ms), and this behavior reduces dramatically as long as the transmission warms up. After 45 min, when TOT reaches around 90?C, the 2-3 shift is very acceptable for my expectations (around 1000ms).

    I already made a complete flush of transmission fluid, but it didnt change this 2-3 behavior. Later, i have added Lubegard Shudder Fix and it really improved all the shifts, but 2-3 was still taking almost 2000ms when TOT is cold.

    Im willing to buy a MPVI3 and start to explore the tuning possibilities. I already read several reports of this 2-3 delay of 6F35 on multiple forums, but didnt find any concrete solution.

    I wonder which shift parameters changes based on TOT... Does somebody have any clue or direction?


  2. #2
    Potential Tuner
    Join Date
    Apr 2022
    I wish I had answers for you, but instead I?m starting down the same path. My MPVI3 arrived yesterday. Have you made any progress?

    Here?s my scenario
    2017 Fusion 2.0 AWD Titanium
    Every shift is great except 2-3
    Very light throttle 2-3 is fine
    WOT 2-3 is fine
    Normal everyday driving 2-3 feels like the converter never unlocked for the shift. It?s enough to spill coffee or watch all your passengers head bob

    Interestingly enough, higher octane or higher ethanol content tends to help the situation a bit. I?m currently running E30. I?ve been curious if there?s a false knock sensor reading that could be contributing? I can?t work out how fuel would have an effect otherwise.

    An good mechanic in my area told me to watch out for very low rpm converter lockup that Ford was using to boost fuel economy numbers.

    I plan to first disable some torque management stuff, and see what happens

  3. #3
    Tuner in Training
    Join Date
    Sep 2023
    Hello friends.
    I have focus 3 1.5ecoboost and same problem.
    Any success?