• 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.


Sonnax drop-in, heavy duty low/reverse modulator sleeve kit is a two-stage valve that ramps the L-R clutch pressure to near double that of an OE valve.

4R100, E4OD

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

Fits '96-later units.

View Instructions Find a Distributor

In Ford 4R100 and E4OD units, 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 heavy duty low/reverse modulator sleeve kit 36947-09K is 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.

  • Innovative dual-valve design controls clutch engagement while nearly doubling holding capacity
  • Hardcoat anodized aluminum valves combat premature wear
  • Newly designed sleeve made from highly wear-resistant aluminum alloy
  • Drop-in Zip Valve parts install quickly and easily
Learn More About Zip Valve™ Drop-In Repairs
  • Modulator Sleeve
  • Orificed Valve
  • Holding Valve
  • Spring
  • 4R100, E4OD Heavy Duty Low/Reverse Modulator Sleeve Kit 36947-09K
  • 4R100, E4OD Heavy Duty Low/Reverse Modulator Sleeve Kit 36947-09K