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  • 1-2 Band burned
  • Low Reverse pressure
  • 1-2 Flare
  • Delayed engagement


These complaints may be caused by the continuous reciprocation of the 1-2 (forward) and reverse servo boost valves wearing the valve body bores.


This oversized, hard-coat anodized aluminum valve restores hydraulic integrity, and has increased valve-to-bore contact to prevent leakage. This valve requires the use of a Sonnax reaming tool kit.

4T60, 4T60-E, 4T65-E

Oversized 1-2 & Reverse Servo Boost Valve Kit
Part No. 84754-40K

Fits either of 2 locations

View Instructions

The continuous stroking of the 1-2 (forward) and reverse servo boost valves wear away at the valve bore, creating excess clearance and reduced apply pressures. This can lead to 1-2 band slippage, delayed engagements, 1-2 shift flares, and decreased reverse pressure. Sonnax has developed an oversized valve 84754-40K that will restore the hydraulic integrity and more than doubles the valve-to-bore contact area to prevent leakage.

  • Valve is manufactured from hard-coat anodized aluminum to prevent future bore wear.
  • Valve will fit both the forward and reverse applications for the 4T60, 4T60-E and 4T65-E

This kit only contains one valve. If both bores need to be repaired, two kits are required.

  • Valve
  • Long Spring
  • Short Spring
  • Coiled Spring Pin

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 thumb

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  • 84754 40k combo
  • 84754 40k