November 24, 2015
When the TCC PWM solenoid is energized and TCC signal fluid pressure is present in GM 5L40-E and 5L50-E, it strokes the TCC regulator valve and regulates line pressure into the converter clutch apply passage. Due to the pulse width modulation of the solenoid, the regulator valve is continuously oscillating. Excess wear at the large spool diameter can prevent proper valve movement, causing no TCC, slips or soft apply. Excess wear at the balance end of the bore can lead to harsh apply. Additionally, the OE valve stops against the TCC PWM solenoid screen, resulting in damage or breakage. Debris from the broken screen can lodge at the Reverse lockout valve, resulting in no Reverse. Sonnax TCC regulator valve kit 55211-04K includes a highly wear-resistant sleeve, modified valve and spring to restore proper converter clutch apply pressure. A solenoid protector is also included to eliminate damage to the solenoid screen. The valve bore must be reamed to accommodate the sleeve.
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Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.