Shift valve 3 kit OS 6HP21/28

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

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.