March 03, 2020
The OE manual valve in GM 4L80-E and 4L85-E transmissions is prone to bending due to its length and relatively narrow spools. Once bent, the valve causes excess bore wear, allowing critical fluid to escape the chosen circuits. This can result in delayed engagement, low line rise and loss of gear.
It is also common for the AFL filter and its end plug to leak, resulting in 2nd gear starts, no upshifts and various trouble codes. Installing improved Sonnax manual valve kit 34994-16K eliminates all these problems and renews AFL and manual circuit pressure control.
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.