The Lineartronic's control system is more complex than a conventional automatic valve body and requires a different diagnostic mindset. Here are the specific components that fail and what correct repair looks like for each. Pulley Pressure Control Solenoids: The TR690 uses two pressure control solenoids — one for the primary pulley and one for the secondary — to control the hydraulic clamping force on the drive chain. These are linear solenoids with very tight manufacturing tolerances. When the primary solenoid degrades (O-ring cracking, spool wear), primary pulley clamping force becomes inconsistent and the CVT hunts for ratio. When the secondary solenoid degrades, chain clamping force under load drops, leading to chain micro-slip under hard acceleration. Both solenoids are located in the valve body assembly and are replaced as individual units — they are not serviceable at the O-ring level in the field. Each runs $85–$130 from a Subaru dealer or quality aftermarket supplier.
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TR690 CVT Valve Body Solenoid Set — Primary and Secondary Pressure Control
Replace both pulley solenoids when opening the TR690 valve body — individual solenoid failure is common but both wear at similar rates and replacing only one is an incomplete repair.
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