November 24, 2015
GM 5L40-E, 5L50-E actuator pressure is supplied to the EPC force motor and shift solenoids. At the force motor it is controlled to react on the boost valve, which is used to control clutch and TCC slippage. AFL pressure is also supplied to the shift solenoids and positions the shift valve accordingly. When AFL pressure is too high, solenoids are flooded and line pressure can be excessive, causing piston or housing fatigue. When AFL is too low, clutches slip and shift valves do not completely stroke. In D ranges, low solenoid pressure can cause the coast clutch to release and distress the forward clutch. In OD 5th Gear range, reduced AFL pressure allows the overdrive clutch to come off or causes 2nd Gear starts. If reduced feed limit pressure is supplied to the safety mode valve, it could remain in the released position, which will make the vehicle operate in 5th Gear only.
Sonnax AFL valve kit 55211-01K includes a highly wear-resistant sleeve, modified valve and spring to restore proper feed limit pressure control. The valve bore must be reamed to accommodate the sleeve.
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