In GM 4L60-E, 4L65-E and 4L70-E unit, severe wear of the TCC regulator valve bore is 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 77754-03K restores normal TCC operation by shoring up the hydraulic integrity of this circuit.
December 22, 2014
December 09, 2014
January 21, 2013
November 20, 2014
September 30, 2005
June 06, 2018
See the Part Selection and Reaming Options Instruction sheet to determine which combined Sonnax parts and tool kits will repair your GM 4L60-E PWM and Non-PWM valve body