In GM 4L60-E, 4L65-E and 4L70-E units, severe wear of the TCC regulator valve bore caused by oscillation of the OE valve allows regulated converter apply pressure to exhaust. This is a primary cause for TCC-related slip code P1870 and overheated converters. Exhausting apply pressure also diminishes line pressure, which can result in burnt clutches. Excess wear at the isolator valve bore reduces TCC apply pressure.

Reconditioning the bore and installing Sonnax TCC regulator and isolator valve kit 77754-04K restores normal TCC operation by restablishing the hydraulic integrity of this circuit.

• Sleeve manufactured from highly wear-resistant aluminum
• Hardcoat anodized aluminum regulator valve combats premature wear
• Isolator valve lengthened to operate in unworn portions of the bore
• Annular grooves help center valves in bore to reduce future side-load wear