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


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 drop-in TCC regulator and isolator valve kit prevents excessive wear and restores these critical bores to their original operating clearances.


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

Fits '93-later units.

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Common complaints with '93-later GM 4T60-E units are falling out of lockup hot, codes 39, 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.

  • TCC regulator sleeve is made from highly wear-resistant aluminum specifically designed to prevent excessive wear
  • Hardcoat anodized aluminum TCC valve combats premature wear
  • 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
  • Drop-in Zip Valve™ parts install quickly and easily
Learn More About Zip Valve™ Drop-In Repairs
  • TCC Regulator Valve
  • TCC Regulator Sleeve
  • Isolator Valve

Sonnax valve body layouts provide a detailed overview of individual units making it quick and easy to determine what’s available for the specific valve body you’re working on. See all Sonnax valve body layouts.

GM 4T60, 4T60-E Valve Body Layout

GM 4T60, 4T60-E Valve Body Layout
  • 4T60-E TCC Regulator & Isolator Valve Kit 84754-01K
  • 4T60-E TCC Regulator & Isolator Valve Kit 84754-01K

You need this if...

4T60-E TCC Regulator & Isolator Valve Kit Vacuum Test Locations