The B1 band in Aisin AW TF-80SC and TF-81SC transmissions is applied in 2^nd and 6^th Gears in conjunction with other clutch packs. As the B1 band control valve oscillates and strokes over time, bore deterioration results which prevents proper hydraulic control of the B1 band. This can cause flares, harsh shifts, slipping, erratic clutch apply timing, ratio codes and a burnt B1 band. Reconditioning the bore and installing Sonnax oversized B1 band control valve kit 39741-48K restores normal shift operation and feel by re-establishing the hydraulic integrity of the B1 circuit.

• New spring matches OE calibration
• Hardcoat anodized aluminum valve combats premature wear
• Annular grooves help center valve in bore to reduce future side-load wear