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  • 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.

4L80-E, 4L85-E

Smart-Tech® Overrun Clutch Valve Kit
Part No. 34200-40K

Fits units '97-later.

View Instructions

Insufficient holding power in the overdrive roller clutch is the underlying cause of chronic overdrive roller clutch failure in hardworking 4L80-E and 4L85-E 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

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.)

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  • 34200 40k web