Load Sensing Valve Adjustment

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Thread: Load Sensing Valve Adjustment

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    Supporter lelandstanford's Avatar
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    Default Load Sensing Valve Adjustment

    According to 2002 Repair Manual Volume 2 (BR-40) that lengthen the adjusting shackle will lower (rear brake) pressure.

    Lengthen the shackle will raise the Load Sensing Spring which has the same effect as bring rear axle closer to the frame. Won't that translates to heavier load and requiring more pressure?

    Used to have a '93 Nissan HardBody and service manual states otherwise.

    2005 Tacoma AC 2WD 2.7L 5M

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    Supporter ricqik's Avatar
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    Default

    In this case lengthen means screwing down on the nut and giving you more distance between the adjuster and truck bed. I (in the case of the repair manual) shorten mine by uncrewing the nut so it is closer to the bed 1" more to compesate for the AAL's.
    '00 tundra
    '06 sequoia
    '98 forester

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    Veteran Member Dude Boy's Avatar
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    I ran a shortened eye bolt on mine when I used the lowering shackles. I didn't want it to "think" there was a heavy load in the bed.

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    Supporter redbaron224's Avatar
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    DudeBoy,

    Your truck doesn't look lowered?
    My Ride: White 2000 Tundra Limited Access Cab, V8, 4WD, TRD with 267,834 miles
    MODS:

    SUSPENSION: front - Cornfed 2" lift, rear - TRD add-a-leafs. EXTERIOR: Ventvisors, UTR bed liner, Reese hitch ELECTRICAL: Alarm and remote start package, Prodigy Brake Controller ENGINE/DRIVETRAIN:Nitto Trail 285/75/R16 wrapped around Mickey Thompson Classics. Cat Back dual custom exhaust with glass packs and 2 1/2" Stainless tips straight back. Air intake box mod.

    Wife's Ride: Gray 2010 Sequoia Limited, 5.7L, 4WD, with 61,104 miles
    MODS:
    EXTERIOR: Weathertech Window Vents

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    Supporter lelandstanford's Avatar
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    Thread Starter

    Default Quote from the Manual

    Here's on BR-40:

    ......
    4. IF NECESSARY, ADJUST FLUID PRESSURE
    (a) Loosen the lock nut.
    (b) Adjust the length of the shackle No. 2.
    Lower pressure: Lengthen A
    High pressure: Shorten A
    Initial set: 120 mm (4.72in.)
    Adjustment range: 112 - 128 mm (4.41 - 5.04 in.)
    HINT:
    One turn of the nut changes the fluid pressure as show in the following specification.
    7 .4 kPa (0.76 kgf/cm, 11 psi)
    (c) Torque the lock nut.
    Torque: 13 N-m (130 kgf-cm, 9 ft-lbf)
    (d) If the pressure cannot be adjusted by the shackle No. 2 raise or lower the valve body.
    Low pressure-Lower body
    High pressure-Raise body
    (e) Torque the nuts.
    Torque: 13N-m (130kgf-cm, 9ft-lbf)
    (f) Adjust the length of the shackle No.2 again.
    If it cannot be adjusted, inspect the valve body.
    ...........

    A is the distance between shackle No. 2's pivot and "eye" of load sensing spring.

    The shackle No. 2 is on the axle connected to load sensing spring. Load sensing valve is mounted on the frame.

    I think the whole algorithm is reversed.

    2005 Tacoma AC 2WD 2.7L 5M

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    Supporter redbaron224's Avatar
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    Default

    I'm guessing your average shadetree mechanic could not adjust this since it must be difficult to measure brake fluid pressure...
    My Ride: White 2000 Tundra Limited Access Cab, V8, 4WD, TRD with 267,834 miles
    MODS:

    SUSPENSION: front - Cornfed 2" lift, rear - TRD add-a-leafs. EXTERIOR: Ventvisors, UTR bed liner, Reese hitch ELECTRICAL: Alarm and remote start package, Prodigy Brake Controller ENGINE/DRIVETRAIN:Nitto Trail 285/75/R16 wrapped around Mickey Thompson Classics. Cat Back dual custom exhaust with glass packs and 2 1/2" Stainless tips straight back. Air intake box mod.

    Wife's Ride: Gray 2010 Sequoia Limited, 5.7L, 4WD, with 61,104 miles
    MODS:
    EXTERIOR: Weathertech Window Vents

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    Veteran Member Dude Boy's Avatar
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    Originally posted by redbaron224
    DudeBoy,

    Your truck doesn't look lowered?
    Mine's on the left in the attached picture.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Default Question: Lift and BPV?

    How does a suspension lift on a tundra affect the BPV (Brake Proportioning Valve)????? Any body run across this concern?

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    Default Re: Load Sensing Valve Adjustment

    it effects the truck by making it think there's less weight on the rear end there fore needing less breaking to possibly avoid a lock up situation it therefore will proportion more breaking effort to the front of the truck and over time if uncorrected will lead to faster wear of the front brake pads and rotors... ask me how I know Oh well it was a good excuse to do the front brake upgrade on mine anyways but i will be dealing with this over the next couple of days I have the factory service manuals but don't have the funds for the sst to measure the break pressures basically the idea is to have the sensing arm at the same position as it was before the lift and that should eleviate this mis proportioning of brakes. Hope this helps.

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    Lurking Member vectervp1's Avatar
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    Default Re: Load Sensing Valve Adjustment

    I haven't done this yet since lifting my truck, but there is an article posted here on how to adjust your proportioning valve to compensate for a lift. Maybe if I get some time this weekend I'll get around to doing it... that and installing my rear Bilstien shocks.

    Here is the thread.

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