Symptoms:

  • Burnt Reverse band
  • Delayed Reverse
  • No Reverse
  • No engine braking in manual low

Cause:

Wear at the #7 low/Reverse checkball seat can result in loss of rear band apply (RBA) pressure due to exhaust of low or RBA pressure in manual 1st or Reverse.

Correction:

Restore hydraulic control and prevent premature wear by installing upgraded material Sonnax #7 low/Reverse checkball seat.

4L80-E, 4L85-E

#7 Low/Reverse Checkball Seat
Part No. 34200-52

Package Quantity: 5

You need this if... Find a Distributor

Vehicles with GM 4L80-E and 4L85-E transmissions commonly exhibit wear in the #7 low/Reverse checkball seat location. This issue is caused by normal movement of the checkball and slight movement of the seat within the bore over time.

As wear progresses, sealing function of the checkball seat becomes compromised and results in loss of rear band apply (RBA) pressure. This can result in a burnt rear band, delayed or no Reverse and loss of engine braking in manual low.

Installing Sonnax #7 low/Reverse checkball seat 34200-52 restores the hydraulic integrity of this circuit to re-establish normal pressure and performance. The checkball seat is made from high-strength, wear-resistant aluminum for added durability.

  • 4L80-E, 4L85-E #7 Low/Reverse Checkball Seat 34200-52
  • 4L80-E, 4L85-E #7 Low/Reverse Checkball Seat 34200-52
  • 4L80-E, 4L85-E #7 Low/Reverse Checkball Seat 34200-52

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 #7 Low/Reverse Checkball Seat Vacuum Test Locations