Sonnax 59947-26K Oversized B4 Release Valve Kit for AW55-50SN/55-51SN Transmissions

The Sonnax 59947-26K oversized B4 release valve kit is designed to restore hydraulic integrity in Aisin Warner 55-50SN and 55-51SN transmissions. This kit eliminates wear-related complaints and sticking valves caused by bore wear at the B4 release valve location.

Common Problems This Kit Addresses:

• Worn B4 release valve bore causing oil pressure loss
• Valve sticking in the bore
• Various 2-3 and 3-2 shift complaints
• Burnt 3rd gear band
• Loss of release pressure and solenoid modulator pressure

Key Features:

• Oversized design restores proper hydraulic integrity to worn bores
• Extended inboard valve spool provides greater stability than OE design
• Enhanced sealing capability at the valve/bore interface
• Also fits AF23/33 and RE5F22A transmission units

The B4 release valve is controlled by solenoid modulator and 4-5 clutch feed pressures to manage the release of the B4 (3rd Gear) band. When the bore becomes worn, pressure can exhaust, resulting in shift complaints and potential band damage. This oversized valve kit provides a permanent solution to restore proper valve function.

Note: Installation requires Sonnax F-59947-TL26 tool kit and VB-FIX reaming fixture (sold separately).