• No engine braking in D1
  • Breakaway of Low/Reverse clutch
  • Burnt Low/Reverse clutch
  • Low/Reverse clutch distress
  • Low pressure


Insufficient L-R clutch holding pressure, due to a minimal area of the modulator plunger valve.


This heavy-duty version is a two-stage valve that ramps the L-R clutch pressure to near double that of an OEM valve.

4R100, E4OD

Heavy Duty Low/Reverse Modulator Sleeve Kit
Part No. 36947-09K

1996 & Later

View Instructions Find a Distributor

The holding capacity of even the largest modulator plunger valve assembly does not supply enough line pressure to the low/reverse clutch to adequately hold the clutch in diesel or heavy-duty applications. This same issue will occur in gas and street applications as the vehicle ages and wear at multiple locations continues to rob line pressure. Sonnax has developed an innovative, dual-plunger valve drop-in replacement assembly that prevents repeated low/reverse clutch distress and burn-up. The inboard, smaller plunger valve has the ratio of the larger OE plunger valve, but functions primarily as the engagement control for the low/reverse clutch. A small orifice along the valve axis prevents harsh or bang engagements by maintaining a controlled feed flow to the larger, outboard holding valve. This valve provides almost double the holding capacity to the low/reverse clutch as the OE valve. Both valves are hard-coat anodized to prevent wear, and the newly designed sleeve is made from a highly wear-resistant grade of aluminum. A new spring is also included to work with the new valves.

  • Innovative dual-valve design controls clutch engagement while nearly doubling holding capacity.
  • Valves are hard-coat anodized to prevent wear.
  • Newly designed sleeve made from highly wear-resistant aluminum alloy.
  • Drop-in-replacement allows for easy and quick installation.
  • Modulator Sleeve
  • Orificed Valve
  • Holding Valve
  • Spring
  • 36947 09k combo
  • 36947 09k