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Symptoms:

  • Harsh Reverse
  • D1 Brake burned
  • Reverse slip

Cause:

Shift valve 3 uses Reverse fluid pressure to regulate line pressure into the D1 brake control circuit. Bore wear caused by valve oscillation can lead to loss of critical Reverse and line pressure and diminish D1 brake control pressure.

Correction:

The oversized Sonnax shift valve 3 allows the bore to be refurbished to restore proper hydraulic clearances, eliminating valuable fluid pressure loss.

ZF6HP21, ZF6HP28, ZF6HP34

Oversized Shift Valve 3 Kit
Part No. 95740-74K

This kit fits M-shift versions of ZF6HP21/28/34 (Generation 2) valve bodies only.


You need this if... View Instructions

Harsh reverse engagement, slippage in reverse or a burned D1 brake can indicate a worn shift valve 3 in vehicles equipped with ZF6HP21/28/34 (Gen. 2) units. In Reverse, the valve uses reverse pressure to regulate line pressure into the D1 brake control circuit. The valve moves under the combined influence of the spring and orificed reverse pressure inboard, which are opposed by reverse pressure outboard. Wear at the inboard spool can reduce apply pressure, causing the D1 brake to slip and burn. Outboard wear lessens the valve's ability to regulate line pressure leading to a harsh D1 apply. Sonnax oversized shift valve 3 kit 95740-74K allows the worn bore to be refurbished, restoring proper hydraulic clearances and eliminating loss of valuable line, reverse and D1 brake control circuit fluid pressures.

  • Valve is hardcoat anodized to reduce wear
  • Spring reproduces OE function with the oversized valve
  • O-Ringed end plug reduces or eliminates end plug leakage

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.

  • Valve
  • Spring
  • End Plug
  • O-Rings (2) 1 Extra

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

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

Topics: Vacuum Testing Vacuum Test Guides Transmission ZF ZF6HP21 Transmission ZF6HP28 Transmission ZF6HP34 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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  • 95740 74k

You need this if...

Vacuum tests at the ports indicated fail to hold the recommended minimum in-Hg.

  • 95740 74k test