April 21, 2021
GM 8L45 and 8L90 units may have TCC apply and release problems. Bore wear or a stuck converter feed limit valve can result in converter overheat, incorrect TCC apply or release, inadequate lube and cooling and converter over-pressurization. Installing Sonnax drop-in converter feed limit valve kit 154740-19K will restore proper valve function, resulting in proper TCC apply and release, regaining control of lube and cooling.
OE vacuum testing at the inboard spool requires converter feed limit vacuum test tool 154740-TL22.
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.
Inboard Location: Install Sonnax converter feed limit vacuum test tool 154740-TL22 with vacuum testing tube attached to long end (Figure 3). Vacuum should hold a minimum of 18 in-Hg (Figures 1 & 3).
Outboard Location: Insert either the OE valve or Sonnax converter feed limit vacuum test tool 154740-TL22 centered in the port (Figure 2). Vacuum at indicated port should hold a minimum of 15 in-Hg (Figures 1, 2 & 3).