Symptoms:

  • 3-2-1 Bump
  • Harsh/No engine braking
  • Clutch failure

Cause:

Wear at the low pressure control valve allows 1-2-3 regulated braking fluid to exhaust.

Correction:

Install Sonnax oversized low pressure control valve kit into a refurbished bore to restore correct hydraulic clearances and prevent future wear.

5L40-E, 5L50-E

Oversized Low Pressure Control Valve Kit
Part No. 55211-17K


You need this if... View Instructions Find a Distributor

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.

  • Hardcoat anodized aluminum valve combats premature wear
  • Outboard spool is 74% longer than the OE design, adding stability and critical hydraulic sealing for the 1-2-3 regulated oil pressure
  • An annular groove has been added to the outboard spool to hydraulically center the valve in the bore and prevent wear
  • Includes oversized end plug
  • Valve
  • Plug

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.

GM 5L40-E, 5L50-E Valve Body Layout

GM 5L40-E, 5L50-E Valve Body Layout
  • 5L40-E, 5L50-E Oversized Low Pressure Control Valve Kit 55211-17K
  • 5L40-E, 5L50-E Oversized Low Pressure Control Valve Kit 55211-17K

You need this if...

Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.

5L40-E, 5L50-E Oversized Low Pressure Control Valve Kit Vacuum Test Locations