Line Pressure Booster Kit
Part No. 4T65E-LB1

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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
Learn More About Zip Valve™ Drop-In Repairs
  • Pressure Regulator Spring
  • Large Ratio Boost Assembly

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.

GM 4T65-E Valve Body Layout

GM 4T65-E Valve Body Layout
  • 4T65-E Line Pressure Booster Kit 4T65E-LB1
  • 4T65-E Line Pressure Booster Kit 4T65E-LB1


Clean Up Your Shifts with Sonnax Line Pressure Booster Kits

We used the 4T65E-LB1 in several applications...it doesn't give harsh shifts, just a little something extra. Very nice product and I highly recommend it.

D. Tucker
Tucker’s Transmission
Sonnax Line Pressure Booster Kit

Sonnax Line Pressure Booster Kits

Crisp, clean shifts without harshness

Sonnax booster kit components are uniquely designed for precision pressure control. At low-end pressures, they deliver normal engagements, normal light throttle shifts and smooth coastdown shifts. When vehicles are pushed harder, components progressively increase pressure for improved clutch holding capacity and increased durability.

Learn more about Line Pressure Booster Kits