sonnax-black Facebook-color LinkedIn-color maillink printlink r_and_r_only SERVOFIX-logo-web Twitter-color VBFIX-logo-web video-logo-web warranty_only Youtube-color


  • Overheated converter
  • Converter shudder
  • Falls out of lockup when hot
  • Code 39, 740, 1870


Low converter apply pressure, caused by a worn regulator valve bore and insufficient isolator boost/PWM oil, or wear at the isolator bore.


The Sonnax redesigned isolator valve and TCC regulator sleeve and valve kit prevents excessive wear and restores these critical bores to their original operating clearances.


TCC Regulator & Isolator Valve Kit
Part No. 84754-01K


View Instructions

Common complaints with a 4T60-E '93-later are falling out of lockup hot, codes 038, 740 and 1870, adverse lockup in cold weather, torque converter shudder and burn-up of the TCC lining. These complaints can be caused by a worn TCC regulator sleeve and/or a worn valve body bore in the isolator valve area. The TCC regulator sleeve design was changed in '93, and this newer design has an aluminum sleeve with a steel valve that continuously oscillates within the sleeve. This motion eventually wears the inner diameter of the sleeve and results in excessive leakage. This leakage allows the TCC apply oil to exhaust to the sump. Leakage also is caused by the hardened steel isolator valve wearing the aluminum valve body bore. This allows converter oil charge reduction and PWM boost oil loss. Install Sonnax TCC regulator and isolator valve kit 84754-01K to resolve these problems.

In some units, wear of the isolator valve bore may be severe enough to require reaming and installing an isolator valve sleeve. The Sonnax isolator valve sleeve 84754-06 is designed to work only with the isolator valve included in 84754-01K. The new sleeve will restore proper function to the isolator valve circuit. Sonnax tool kit 84754-TL6 provides the necessary tooling to refinish the isolator valve bore in '93-later 4T60-E units.

  • TCC regulator sleeve is made from highly wear-resistant aluminum specifically designed to prevent excessive wear
  • Closely toleranced TCC valve is made from hard-coat anodized aluminum to prevent wear and restore hydraulic integrity
  • Isolator valve is longer than OE in order to contact the entire length of the valve bore
  • Larger spool diameter and feed orifice have been added to the isolator valveto allow PWM oil to increase TCC oil boost
  • Isolator valve sleeve salvages valve bodies with excessively worn isolator valve bores which are not corrected by the use of 84754-01K alone
  • TCC Regulator Valve
  • TCC Regulator Sleeve
  • Isolator Valve

September 30, 2005

Anatomy of a Transmission: Oil Flow in the Pump-PR-Converter-Cooler Lube Circuits

Gregg Nader

Topics: Diagnostics And Theory Transmission

Read Now
  • 84754 01k combo
  • 84754 01k