Required tool kit F-85755-TL9 is no longer in production. Check with your distributor for availability.
The pressure reduction valve in the ZF5HP19, ZF5HP19FL and ZF5HP19FLA units is designed to limit solenoid feed oil pressure. Wear in the bore and on the valve spools can cause the feed oil pressure to be high or low depending on the severity and location of the wear. Wear at the balance end contributes to high pressure and harsh shifting, while wear around the regulating and limit spools will tend to cause clutch slippage and failure. Installation of the Sonnax oversized pressure reduction valve kit 85755-09K will restore OE pressure control and limits to the solenoid feed circuits.
Vacuum tests at the ports indicated fails to hold the recommended minimum of in-Hg