Symptoms:

  • Code 894, 1870
  • TCC cycling
  • TCC slip
  • 3-4 Clutch failure

Cause:

Severe wear of the TCC regulator bore allows regulated converter apply pressure to exhaust, while wear at the isolator valve bore reduces TCC apply pressure.

Correction:

This isolator sleeve kit combined with Sonnax TCC regulator valve kit helps restore normal TCC operation.

4L60-E, 4L65-E, 4L70-E

Isolator Sleeve Kit
Part No. 77754-ISO


You need this if... View Instructions Find a Distributor

Severe wear of the TCC regulator valve bore from the OE valve allows regulated converter apply pressure to exhaust. This is a primary cause for a TCC-related 1870 slip code and overheated converters. Exhausting apply pressure also diminishes line pressure, which results in burnt clutches. Excessive wear at the isolator valve bore reduces TCC apply pressure. The Sonnax isolator sleeve kit 77754-ISO in combination with Sonnax TCC regulator valve kit 77754-03K or 77754-04K allows you to restore hydraulic integrity of the apply circuit. Sleeve is manufactured from highly wear-resistant aluminum to provide full support for the valve and prevent side loading.


  • 4L60-E, 4L65-E, 4L70-E Isolator Sleeve Kit 77754-ISO
  • 4L60-E, 4L65-E, 4L70-E Isolator Sleeve Kit 77754-ISO

You need this if...

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