Only some Aisin AW 55-50SN and 55-51SN transmissions ('05-later units installed in Nissan and GM vehicles) were equipped with a control spring in the B5 clutch control valve line-up. Using a valve body without a spring in those vehicles creates a mismatch between the B5 lineup and the TCM calibration, often causing a harsh 2-3 upshift or 3-2 downshift. Sonnax B5 control spring 59947-33 is a direct replacement for the OE spring. This allows rebuilders to rebuild any suitable core for use in vehicles where the spring is required, or correct shift concerns caused by a missing spring.

Restores valve train response, matching the TCM calibration
Allows any AW55-50SN valve body to be converted to a spring type application

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