Symptoms:

  • Low line pressure
  • Delayed Forward
  • Harsh shifts
  • 2-3 Flare
  • Erratic SLT pressure

Cause:

Line pressure control accumulator pistons are leaky, jammed or bound.

Correction:

Sonnax LPC accumulator piston is made of aluminum to match the expansion rate of the aluminum valve body (OE was steel). The piston restores SLT pressure and dampening. SLT is the boost pressure in this unit.

55-50SN, 55-51SN

LPC Accumulator Piston Kit
Part No. 59947-LPC

Also fits AF23/33 and RE5F22A units.

View Instructions Find a Distributor

In Aisin Warner 55-50SN and 55-51SN transmissions, bore wear at the Line Pressure Control (LPC) accumulator bore is common. Throttle pressure (SLT) acts on this piston in all gears, which moves the piston against the springs to dampen any pressure irregularities in the SLT circuit. Wear in the bore can allow SLT pressure to exhaust, and creates ridges that cause the piston to jam or bind in the bore. Either results in the inability of SLT dampening, which can create erratic SLT pressure, low pressure, delayed shifts, and various flared and harsh shifts. Sonnax LPC accumulator piston kit 59947-LPC provides positive seals on both ends of the piston to seal worn bores, and prevent the metal-to-metal contact between piston and bore that can result in sticking issues.

  • O-Rings eliminate fluid leakage between LPC piston and bore
  • O-Rings eliminate metal-to-metal contact between piston and bore that causes wear
  • Piston Sleeve
  • Spring Small
  • Spring Large
  • O-Rings (2)

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.

Aisin AW 55-50SN, 55-51SN Valve Body Layout

Aisin AW 55-50SN, 55-51SN Valve Body Layout
  • 55-50SN, 55-51SN LPC Accumulator Piston Kit 59947-LPC
  • 55-50SN, 55-51SN LPC Accumulator Piston Kit 59947-LPC