Description:
A Gen 3 XY Shifter Kit, New Exch K-3784 is a heavy-duty truck transmission component, not a typical car “shifter.” It’s used in automated manual transmissions—especially Eaton Fuller gearboxes found in semi-trucks. Gen 3 XY Shifter Kit, New Exch (Heavy)  For Heavy-duty Eaton Corporation / Fuller automated manual transmissions (Eaton Fuller UltraShift,Eaton Fuller UltraShift PLUS,Eaton Fuller AutoShift)

Part Number: K-3784, K-3784RX
Condition: New
Manufacture/Brand: Eaton

Fits K-3784 For Heavy-duty Eaton Corporation / Fuller automated manual transmissions (Eaton Fuller UltraShift, Eaton Fuller UltraShift PLUS, Eaton Fuller AutoShift),specifically for heavy-duty (HD) transmissions, not medium-duty.

Purpose of using K-3784:

1. Gear selection (X-axis)

  • Moves side-to-side to choose the correct gear rail
  • Example: switching from the 3–4 rail to the 5–6 rail

2. Gear engagement (Y-axis)

  • Pushes/pulls to physically engage the selected gear

3. Position feedback

  • Uses sensors to tell the transmission controller:
    • What gear it’s in
    • Whether the shift completed correctly

 

Signs of a Bad Gen 3 XY Shifter Kit K-3784:

1. Won’t shift or gets stuck in neutral

  • Truck won’t go into gear from a stop
  • May stay stuck in neutral even with throttle applied
  • One of the most common failure symptoms

2. Hard, delayed, or missed shifts

  • Rough gear engagement
  • Long delay between gears
  • Skips gears or fails to complete shifts

3. Transmission fault codes / warning lights

  • “Service Transmission” warning
  • Check engine light related to transmission
  • Common in trucks using Eaton Fuller UltraShift or AutoShift systems

4. Gear display issues

  • Dashboard shows wrong gear
  • Gear indicator flashes or shows “—”
  • Indicates position sensor problems inside the shifter

5. Intermittent shifting problems

  • Works fine sometimes, fails other times
  • Often caused by:
    • Internal motor wear
    • Sensor failure
    • Wiring/connection issues

6. Stuck in one gear (limp mode)

  • Truck locks into a single gear (usually 3rd or 5th)
  • Designed to let you limp to a shop

7. Clicking or no movement sound

  • You may hear:
    • Clicking but no shift (motor trying but failing)
    • Or no sound at all (dead actuator)