4L80-E, 4L85-E

Line Pressure Booster Kit

Part No.


Line Pressure Booster Kit
  • 4l80e-lb1_combo

  • Line Pressure Booster Kit

Small_4l80e-lb1_combo Small_4l80e-lb1

4L80-E, 4L85-E

Line Pressure Booster Kit

Part No. 4L80E-LB1

  • Large Ratio Boost Assembly
  • Pressure Regulator Spring
  • O-Rings (2)

Sonnax hydraulic line pressure booster kits contain stronger pressure regulator springs and large ratio boost valves designed to work together to provide progressive pressure increases as driving conditions become more demanding.

Our pressure regulator springs are approximately 10% stronger than OE and more conservative in impact than other aftermarket kit springs. Large ratio boost valves provide higher pressure incrementally and when it is needed the most. The combination of these springs and valves in a Sonnax kit gives you the best of both worlds: a modest pressure increase at the low end, with a high-end pressure that is equal to or greater than that of other aftermarket kit springs.

  • Achieve shorter shifts and increased torque capacity without creating low-speed harshness
  • Improved band and clutch holding capacity for increased durability
  • Progressive pressure increase as driving conditions become more demanding
  • All the benefits of increased line pressure without overloading the pump at idle
  • Simple and affordable drop-in solution with no special tools or reaming required.

The Prescription for Optimum Pressure

Stronger pressure regulator springs raise pressure equal amounts at idle and maximum pressure. Many aftermarket “kit” springs are a compromise, raising pressure too much at idle and not enough at maximum pressures. Larger boost valves, on the other hand, have a progressive effect on pressure, changing the rate of pressure increase.

The Sonnax large ratio boost valves and stronger pressure regulator springs are designed to work together. This is an ideal combination: smooth engagements and lower load on the pump at idle, but a greater increase in pressure as the transmission is worked harder. For a more in-depth look at raising line pressure, read The Prescription for Optimum Pressure.

Learn More

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The Prescription for Optimum Pressure

Contact a Sonnax Distributor to purchase this part.