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.
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.
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.
January 14, 2014
Topics: Identification Guides Transmission Ford ZF ZF6HP19 Transmission ZF6HP26 Transmission ZF6HP32 Transmission ZF6HP21 Transmission ZF6HP28 Transmission ZF6HP34 Transmission 6R80 Transmission 6R60 TransmissionRead Now
December 21, 2012
Topics: Vacuum Test Guides Vacuum Testing Transmission ZF ZF6HP21 Transmission ZF6HP28 Transmission ZF6HP34 TransmissionRead Now
September 30, 2005
Topics: Diagnostics And Theory TransmissionRead Now
Contact a Sonnax Parts Distributor.
Vacuum tests at the ports indicated fail to hold the recommended minimum in-Hg.