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Thread: 4l80e force motor line pressure adjustment

  1. #1
    Tuner in Training
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    Oct 2017
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    14

    4l80e force motor line pressure adjustment

    I have a 2002 4l80e hd2 shift kit with out their pressure relief mod instead i used sonnax boost valve new clutches and steels new pump and new seals i did replace the direct drum housing because it was grooved [damaged] any way i finally got back in my vehicle and the transmission works all foward gears and reverse but... when accelerating from idle in drive i get slippage. I hooked up a gauge and in reverse i get 90-100 psi and in drive i get 70-80 ,,, if i go 30% throttle while in reverse i get roughly 220 -230 psi on the gauge and when i do the same for drive i get roughly 140-150 at the most im interested in increasing the pressure on drive i would like to know how to add 10-15 % more psi to the force motor table or what will be the best way to do so ive heard i can turn the force motor screw a 1/4 to achieve this is this correct ?
    The only thing that i can see is that the direct drum housing counter part , ex: the part that has the four seals had slight minor damage on the upper part of it due to it rubbing against the housing but nothing major the seals were good so i reused it im wondering if that will affect the foward gears to the point that it wont hold 1st gear even at 30% throttles basically i cant due a burn out with it slipping 🤷*♂️ Soo can anyone help me up the force motor table in percent form as it only has X + and = but i dont see a percent option i would like to start at 10% across the board
    Here are the pics of what im talking about the piece with the four teflon ring where the yellow marking is right after the last teflon seal the metal was slightly shaved nothing major but enough to be noticeable would that cause a leak to where 1 st gear would not hold 🤷*♂️

  2. #2
    Senior Tuner Frost's Avatar
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    Jan 2006
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    Richmond VA
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    So, being honest, trying to work around a physical problem with software like this is almost never the way to go. You know that your physical line is low in forward gears..

    Ok and with that said, the force motor current table is the final lookup for the current needed to generate the specified pressures via the PCS. LOWERING this table will RAISE the pressure returned by all requests. Multiplying the whole table by 0.90 is your 10% change (at table level, not gonna be the same IRL physical).

    Also realize that this is not selective... it's going to crank things up in Reverse as well. You really just need to address the issue in the trans though. That pressure is low.
    Steve Williams
    TunedbyFrost.com