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  • 5-4 Flare
  • 5-4 Neutral
  • No 4-5
  • VFS 1/A solenoid control code
  • Delayed Forward
  • Harsh Forward


OE boost sleeve wears prematurely, allowing critical pressure loss and/or seizure of valve within sleeve.


Recover hydraulic control and renew shift performance by installing Sonnax clutch A & E control boost valve kit.

ZF6HP21, ZF6HP28, ZF6HP34

Clutch A & E Control Boost Valve Kit
Part No. 95740-28K

Sevices 2 bores

You need this if... View Instructions

ZF6HP21/28/34 (Generation 2) transmissions are equipped with an aluminum sleeve for the clutch A and E control boost valve. This material is prone to wear from valve plunger reciprocation. Failure of this sleeve results in a variety of shift problems and solenoid codes. The Sonnax clutch A and E control boost valve kit 95740-28K will restore the correct hydraulic clearance and proper function of the assembly.

  • Hardcoat anodized aluminum valve combats premature wear
  • Sleeve is highly wear-resistant to increase service life

Kit is NOT compatible with ZF6HP19/26/32 (Gen.1) units. To differentiate between Gen. 1 and Gen. 2 valve bodies, see ZF Identification Guide.

  • Valves (2)
  • Sleeves (2)

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.

ZF6HP21/28/34 (Generation 2) Valve Body Layout

Zf6hp21 28 34 gen 2

January 14, 2014

ZF6HP19/26/32 (Generation 1), Ford 6R60, 6R75, 6R80, ZF6HP21/28/34 (Generation 2) Identification Guide

Topics: Identification Guides Transmission Ford ZF ZF6HP19 Transmission ZF6HP26 Transmission ZF6HP32 Transmission ZF6HP21 Transmission ZF6HP28 Transmission ZF6HP34 Transmission 6R80 Transmission 6R60 Transmission

Read Now

December 21, 2012

ZF6HP21/28/34 (Gen. 2) Vacuum Test Guide

Topics: Vacuum Test Guides Vacuum Testing Transmission ZF ZF6HP21 Transmission ZF6HP28 Transmission ZF6HP34 Transmission

Read Now
  • 95740 28k combo
  • 95740 28k
  • 95740 28k details

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.

  • 95740 28k test