Symptoms:

  • Soft shift & low accumulator pressure
  • High line pressure in Drive
  • Low line rise in Reverse

Cause:

Wear of the accumulator control bore and valve spool causes low accumulator pressure that results in soft shifts.

Correction:

Ream the valve bore and install the Sonnax oversized valve, matched spring and oversized end plug.

4L80-E, 4L85-E

Oversized Accumulator Control Valve Kit
Part No. 34994-22K


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

In GM 4L80-E and 4L85-E units, the accumulator control valve controls shift firmness by managing accumulator back pressure. Wear at the valve or bore can lead to multiple symptoms, the most common being reduced line pressure in Reverse, elevated line pressure in Drive, and soft or harsh upshifts depending on location and magnitude of wear. When valve/bore wear allows cross-leakage of torque signal/boost oil to exhaust to the sump, line pressure drops causing soft shifts. Alternatively, when bore wear allows Drive oil to enter the torque signal passage, line pressure increases and shift feel hardens.

Reconditioning the bore and installing Sonnax oversized accumulator control valve kit 34994-22K restores hydraulic integrity of this circuit to re-establish normal shift operation and performance.

  • Upgrade '91–'96 4L80-E accumulator control valve to '97-later calibration
  • Restore OE accumulator control valve response in '97-later units
  • Valve
  • Spring
  • End Plug
  • 4L80-E, 4L85-E Oversized Accumulator Control Valve Kit 34994-22K
  • 4L80-E, 4L85-E Oversized Accumulator Control Valve Kit 34994-22K

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.

4L80-E, 4L85-E Oversized Accumulator Control Valve Kit Vacuum Test Locations