• OD roller clutch failure
  • No Forward
  • 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 Find a Distributor

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
Range Gear Overrun Clutch with
Sonnax 34200-40K
Clutch Valve Kit
Overrun Clutch
with OE
Clutch Valve
Park Applied
Reverse Applied
Neutral Applied
Overdrive 1st Applied
2nd Applied
3rd Applied
Drive 1st Applied Applied
2nd Applied Applied
3rd Applied Applied
D2 1st Applied Applied
2nd Applied Applied
D1 1st Applied Applied

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