Bosch Rexroth 4WRLE Valve, Comparing Old vs. New Model | Tech Talks

What the video covers

• Practical comparison and replacement guidance for the Bosch Rexroth proportional directional valve 4WRLE:
  • The long‑standing “3x” generation (1990s design) versus the newer “4x” replacement.
  • Presented by Rob Panzarello of Airline Hydraulics for technicians and engineers who need to swap obsolete 3x valves for 4x units.

Key similarities

• Functional/spool compatibility: spool types and command mapping (for example E‑spools, W‑6) and the control logic remain the same across generations.
• Electrical pin functions: the seven signal/power/feedback pin assignments are retained (A/B power, D/N/E control signals, plus a feedback pin), so wiring logic is compatible.

Major differences and impacts

• Connector
  • Physical connector changed from a mini‑DIN style to a standard M12.
  • Pin functions are the same, but the new M12 is easier to source and field‑wire. Be mindful of mating cables/adapters.
• Feedback electronics
  • Feedback sensor/electronics are updated and tied to a new board design.
  • Older units used different voltage conventions; this may prevent direct reuse of feedback assemblies or board‑level replacements.
• Pilot/drain model coding
  • Functionally the internal/external pilot and drain ports are the same, but the 4x model code uses different letters:
    • Internal pilot/drain on 4x: P and T (pilot from P, drain to T).
    • External pilot/drain on 4x: X and Y (ports in the manifold).
  • Verify the model code carefully when ordering replacements.
• Hydraulic performance
  • Improved flow: on a size 16 valve the old 3x flowed ≈180 L/min at a 10 bar pressure drop; the 4x flows up to ≈200 L/min at the same ΔP (roughly a 10–20% increase) thanks to casting/design improvements that reduce pressure drop.
• Mechanical / mounting
  • Bolt heights changed — example: size 16 requires bolts ≈9 mm longer for the 4x.
  • A bolt/height chart is available for sizes 10–35. Verify bolt lengths and clearances before swapping.

Practical replacement checklist (from the video)

1. Confirm spool type and command mapping (these remain the same).
2. Verify electrical pin functions and obtain the proper M12 cable or an adapter.
3. Check feedback device/electronics compatibility; be prepared that board‑level parts for 3x may be unobtainable.
4. Confirm pilot/drain port configuration — interpret the 4x model code (P/T vs X/Y).
5. Measure and order correct bolt lengths (consult the size chart).
6. Expect slightly higher flow capacity; plan to test and tune the system if needed.

Recommendation: When converting 4WRLE 3x → 4x, pay particular attention to connector type, feedback electronics, pilot/drain coding, and mounting bolt length to ensure a functional swap. Contact the manufacturer or an authorized specialist if uncertain.

Main speaker / source

• Rob Panzarello — Airline Hydraulics
• Subject manufacturer: Bosch Rexroth (4WRLE valves)