• 2nd Gear starts
  • Gear ratio codes
  • Low line pressure
  • High line pressure
  • TCC slip
  • No 4th
  • No 5th
  • Forward clutch distress
  • OD clutch distress
  • Coast clutch distress


Wear at the AFL bore reduces line rise and solenoid pressure.


This kit includes a wear-resistant sleeve, modified valve and spring to re-establish feed limit control.

5L40-E, 5L50-E

AFL Valve Kit
Part No. 55211-01K

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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.

  • Highly wear-resistant sleeve provides significantly more valve support to reduce leakage and prevent wear
  • Anodized aluminum valve resists wear to prevent leakage
  • Contoured valve stem significantly decreases fluid flow influence over limiting pressure
  • Annular grooves added to the valve properly center it within the sleeve, preventing wear due to side loading
  • Replacement spring limits feed limit pressure to 115 psi for proper pressure control
  • Sleeve
  • Valve
  • Retaining Clip
  • Spring

Sonnax valve body layouts provide a detailed overview of individual units making it quick and easy to determine what’s available for the specific valve body you’re working on. See all Sonnax valve body layouts.

GM 5L40-E, 5L50-E Valve Body Layout

GM 5L40-E, 5L50-E Valve Body Layout
  • 5L40-E, 5L50-E AFL Valve Kit 55211-01K
  • 5L40-E, 5L50-E AFL Valve Kit 55211-01K