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Manufacturer Part Number: 84880M-01

Brand: Sonnax

Fitment Type: Direct Replacement

Manufacturer Warranty: Yes


3-4 Accumulator Piston
Part No. 84880M-01

It is common to have poor 3-4 shifts, no 4th Gear or a burned 4th clutch in GM 4T65-E units. This can be caused by excess wear at the 3-4 accumulator piston pin bore, which allows 4th clutch oil to exhaust and can result in harsh 4th, no 4th Gear or a burned 4th clutch. Pin bore wear also reduces 3rd clutch pressure during 3-4 shift. The 4th shift quality depends on the condition of the piston and accumulator valves. If the 4th accumulator piston seizes, the 4th shift will be very hard. Sonnax 3-4 accumulator piston 84880M-01 restores accumulator pressure and eliminates cross leaks.

  • Piston is manufactured from high-grade billet aluminum to prevent wear
  • Tight tolerances and surface finish restore proper clearances
  • Piston accepts OE or standard replacement D-ring


  • 3-4 Concerns
  • 4th Clutch burned
  • Soft 3rd
  • No 4th


Wear at the 3-4 accumulator piston pin or bore.


Sonnax 3-4 accumulator piston is made from high grade billet aluminum to prevent wear and restores clearances at the pin.

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