• TCC codes
  • TCC apply & release concerns
  • Converter shudder
  • Burnt converter


TCC regulator valve bore wear allows loss of crucial apply pressure.


Recover hydraulic control and renew TCC performance by installing Sonnax TCC regulator valve kit.

4L80-E, 4L85-E

TCC Regulator Valve Kit
Part No. 34994-01K

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

GM vehicles equipped with 4L80-E and 4L85-E transmissions may exhibit problems such as TCC shudder, burnt converter linings, TCC apply and release concerns and related codes. These issues can often be caused by critical pressure loss due to excess wear in the TCC regulator bore. Installing Sonnax TCC regulator valve kit 34994-01K shores up the hydraulic integrity of the TCC control circuit to return robust TCC operation.

  • Hardcoat anodized aluminum valve combats premature wear
  • Lengthened critical spool for added stability and wear prevention
  • Annular grooves help center valve in bore to reduce future side-load wear
  • Added chamfer to improve apply characteristics and prevent shudder
  • Two springs included in kit; one for OE lockup feel, the other provides firmer-than-OE
  • Valve
  • Spring .420" O.D.
  • Seal Scarf-Cut
  • Spring .300" O.D.

February 21, 2013

GM 4L80-E Vacuum Test Guide

Topics: Vacuum Test Guides Vacuum Testing Transmission GM 4L80-E Transmission

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September 30, 2005

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

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Topics: Diagnostics And Theory Transmission

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  • 34994 01k combo
  • 34994 01k

You need this if...

Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.

  • 34994 01k test