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  • Burnt brake clutches
  • Burnt clutches
  • Delayed Forward
  • Delayed Reverse
  • Soft upshifts


Wear of the boost valve sleeve allows leakage and cross leakage of the Reverse, EPC and Cutback circuits.


This patent pending Sonnax boost valve kit restores the hydraulic integrity of the circuits and replaces all three OE ratios.

A340E, A340F

Dual-Ratio Boost Valve Kit
Part No. 97741-01K

Fits '00-later V6 & V8, late-style, Type 3 & 4 valve bodies.

You need this if... View Instructions

In Toyota/Lexus A340E & A340F late-style units the OE steel cutback/EPC and reverse boost valves wear the inside diameters of the cast aluminum boost sleeve due to continuous reciprocation as they provide biasing force to adjust main line pressure. This wear allows critical Reverse, EPC and Cutback fluid pressures to leak or cross leak, creating numerous drivability complaints and part failures.

Replacing the OE assembly requires matching the correct valve spool ratio (three-dot, two-dot or no-dot sleeve) (Figure 1) to ensure proper line pressure. The Sonnax dual-ratio boost valve kit 97741-01K not only restores hydraulic integrity, but also provides for all OE ratios in one assembly. By selecting either the large diameter priority or small diameter priority EPC boost valve and adding optional shims to the OE pressure regulator valve spring face, all three of the OE ratios can be achieved with the one assembly.

• Sleeve is made from high-quality aluminum for wear resistance

• Valve is hardcoat anodized to reduce wear

• Unique priority diameter design allows for dual ratio in one assembly

• Additional shims allow for tuning to the third OE ratio

  • Boost Sleeve
  • Cutback Boost Valve
  • Reverse Boost Valve
  • Shim .032" thick, Selective
  • Shim .015" thick, Selective
  • EPC Boost Valve Small Dia. Priority
  • EPC Boost Valve Large Dia. Priority

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.

Toyota/Lexus A340E/F Valve Body Layout

A340e f vbl thumb

January 16, 2014

Toyota A340E/F Identification Guide

Topics: Identification Guides Transmission Toyota/Lexus A340E Transmission A340F Transmission

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August 21, 2013

Toyota A340E/F, '00-Later Vacuum Test Guide

Topics: Vacuum Testing Vacuum Test Guides Transmission Toyota/Lexus A340E Transmission A340F Transmission

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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.

  • 97741 01k test