November 24, 2015
In GM 5L40-E and 5L50-E units, the low pressure control valve applies in 1st, 2nd or 3rd Gear coast conditions, when engine braking is needed. Depending on the gear and solenoid states, 1-2-3 regulated fluid pressure is routed through this valve to provide engine braking through a controlled apply of the low/reverse clutch, 2nd coast clutch or OD clutch. If the bore has excessive wear, this regulated oil pressure is open to exhaust, resulting in 3-2-1 bumps on coast downshifts, no engine braking, and/or clutch failure.
Sonnax oversized low pressure control valve kit 55211-17K is easily installed into a refurbished bore and incorporates design upgrades to prevent future wear concerns.
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.
Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.