Number 34200-40K Sonnax 4L80E Smart-Tech Overrun Clutch Valve Kit Fits 1997-later.

$ 162.99

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Insufficient holding power in the overdrive roller clutch is the underlying cause of chronic overdrive roller clutch failure in hardworking 4L80E and 4L85E transmissions. When the roller clutch fails, the damage can be catastrophic and the only fix is replacing the drum, planetary assembly and mating components.

The Sonnax Smart-Tech overrun clutch valve kit 34200-40K offers a hydraulic solution to this known mechanical problem. This patent-pending kit keeps the overrun clutch applied, allowing the clutch to share a load the OD roller clutch otherwise struggles with on its own.

  • Improves OD roller clutch holding power in lower gears
  • Extends the life of workhorse transmissions while preventing warranty claims and comebacks
  • Installs quickly onto the valve body — no transmission removal needed


  • No Forward
  • OD roller clutch failure
  • Overrun clutch distress


Lack of sufficient holding power in the overdrive roller clutch.


Apply the overrun clutch at all times, reinforcing the roller clutch to adequately support heavy loads.

Any other modifications to the valve body should be completed prior to installing Sonnax Smart-Tech® overrun clutch valve kit.

  • Socket-Head Cap Screw Long
  • Socket-Head Cap Screws (2) Short
  • Button-Head Screws (2)
  • Retaining Pins (2)
  • Valve Manifold
  • Short Tube
  • Long Tube
  • S-Shaped Bracket
  • Flat Bracket
  • L-Shaped Bracket
  • Gasket
  • End Plug
  • Valve
  • Spring
  • Sleeve
  • Tabbed Bore Plug
  • O-Rings (3) 1 Extra
  • Cap Plugs (2)
  • Aluminum Plugs (2) Small
  • Alignment Pins (2)
  • Drill Jig
  • Drill Bit Small (.109″ dia. )
  • Drill Bit Large (.180″ dia.)


Additional information

Weight 5 lbs
Dimensions 8 × 8 × 4 in