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  • Repeated clutch failure
  • Soft upshifts
  • High line pressure in Reverse
  • Delayed engagement
  • Erratic line pressure
  • Low line pressure in Reverse
  • Low line rise


Severe wear of the boost sleeve allows TV and boost oil leakage.


The replacement boost valve and sleeve assembly restores hydraulic integrity and prevents cross leaks.


This kit replaces OE valves with .566" and .523" dia. spools. Measure the OE valve and compare dimensions to ensure correct part is ordered.

Part Number Large Spool Small Spool
97855-23K .566 dia. .523 dia.
97855-30K .546 dia. .480 dia.

A340, A340E, A340F, A340H

Boost Valve Kit
Part No. 97855-23K

View Instructions

The steel OE valve in Toyota/Lexus A340, A340E/F/H type 1 transmissions moves within the cast aluminum sleeve, wearing the sleeve. After this wear becomes severe, the valve no longer operates properly, causing soft upshifts and delayed engagement. Sonnax boost valve kit 97855-23K will restore proper operation.

  • Sleeve made from high-quality aluminum for better wear resistance
  • Hardcoat anodized aluminum valve combats premature wear
  • Valve
  • Sleeve
  • Shims (3)

January 16, 2014

Toyota A340E/F Identification Guide

Topics: Identification Guides Transmission Toyota/Lexus A340E Transmission A340F 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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  • 97855 23k