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


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


This 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 AW55-51SN, AF 23/33and RE5F22A units.

You need this if... View Instructions
  • 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
  • Springs (2)
  • 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 Valve Body Layout

Aw55 50sn vbl thumb

December 22, 2014

The Art of the Silver Bullet

Tory Royce

Topics: Diagnostics And Theory Shop Practices Rebuilding Tips Vacuum Testing Transmission GM Aisin AW 4L60-E Transmission 55-50SN Transmission

Read Now
  • 59947 lpc combo
  • 59947 lpc

You need this if...

Vacuum test at the cover exhaust hole or accumulator entry port is below 18" of vacuum.

  • 59947 lpc test