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8.3 Air Lockers

ARB air-operated locking differentials for the front Dana 60 and rear Sterling 10.5 axles.

Front Model: ARB RD166 (Dana 60, 35 spline, 4.56 & up)

Rear Model: ARB RD140 (Ford 10.25/10.5 Corporate Sterling, 35 spline)

Front Locker Control: SwitchPros OUTPUT-17 (low-side driver, 2A)

Rear Locker Control: SwitchPros OUTPUT-10 (15A output, 2A draw)

Air Source: ARB Twin Compressor via manifold

Specifications

Spec Front Locker Rear Locker
Model ARB RD1661 ARB RD1402
Axle Dana 60 Sterling 10.5
Spline Count 35 35
Gear Ratio 5.13 5.13
Carrier Series 4-series (4.56 & up) All ratios
Solenoid Draw ~2A ~2A
SwitchPros Output OUTPUT-17 (low-side) OUTPUT-10 (15A)
SwitchPros Button Button 9 Button 10

Front Gear Thickness

RD166 is the 4.56-and-up carrier. The Revolution 5.13 gear must be standard thickness. Do not order D60-513RT (thick) or the REV-F350-513-K package.

Rear RD140 fitment with the 10.25" gear in the 10.5 housing: TBD #300.

Wiring

Solenoid Control

Locker SwitchPros Output Wire Route
Front OUTPUT-17 18 AWG Firewall → driver frame rail → front axle
Rear OUTPUT-10 18 AWG Firewall → cabin trunk → rear axle

Wire Routing

  • Front Locker (OUTPUT-17): SwitchPros (firewall, cabin side) → along driver frame rail → front axle solenoid; path and length TBD #81
  • Wire: 18 AWG (2A load, low-side driver output)
  • Protection: Split loom, P-clamps every 18", secure to frame rail
  • Rear Locker (OUTPUT-10): SwitchPros (firewall, cabin side) → H5 rear bundle through the cabin trunk → rear axle solenoid; length TBD #63
  • Wire: 18 AWG (2A load)
  • Protection: Split loom where exposed, secure to axle housing

Air Line Routing

Air Line Installation

Air lines from manifold must be routed to both axles with proper protection from heat, abrasion, and road debris.

Line Route Length
Front Locker Manifold (under seat) → along driver frame rail → front axle ~12 ft
Rear Locker Manifold (under seat) → rear axle ~6 ft

Air Line Specifications:

  • Type: ARB air line kit (1/4" OD nylon tubing, 200 PSI rated)
  • Fittings: Push-to-connect fittings at manifold and locker ends

Protection:

  • Split loom over entire run where exposed to road debris
  • P-clamps every 12" along frame rail
  • High-temp silicone sleeve where crossing near exhaust (6" minimum clearance)
  • Rubber grommets at body/frame penetrations

Axle Travel Slack

Leave service loops at both axles sized for full droop on the ORI struts. Measure at full droop, not at ride height. Loop length: TBD #303.

Operation

Engagement Sequence

Press and hold the button to open the solenoid; pressurized air locks the differential instantly (no waiting for compressor). Release to disengage.

Locker Button SwitchPros Output
Front Button 9 OUTPUT-17
Rear Button 10 OUTPUT-10

Tank refill after locker use is automatic — see Air Compressor: Automatic Pressure Control for the pressure switch logic.

Safety Considerations

Locker Operation

  • Only engage lockers at low speeds (typically <5 mph)
  • Disengage lockers before returning to normal speeds
  • Never engage lockers on dry pavement
  • Ensure adequate air pressure before engaging lockers

Outstanding Items

High (1)

  • ARB RD140 fitment with Revolution F10.25-513L in the Sterling 10.5 housing (#300) — The rear runs a 10.25" ring gear (Revolution F10.25-513L) in the 10.5 housing with the ARB RD140 carrier (Ford 10.25/10.5, 35 spline, all ratios). Confirm with ARB or Revolution that the RD140 flange and ring gear bolt pattern match the F10.25 gear in this housing before ordering, and confirm the pinion depth starting point (owner note: add roughly 0.120" to the pinion depth stack).

📋 Medium (3)

Build Tasks

  • Verify RD166 against the Revolution D60 reverse 5.13 standard thickness gear
  • Order ARB air line installation kit with 1/4" fittings for front/rear

  1. ARB RD166 — Air Locker, Dana 60HD, 35 spline, 4.56 & up (4-series carrier). Revolution Gear listing, accessed 2026-09-16. ↩

  2. ARB RD140 — Air Locker, Ford 10.25/10.5 Inch, 35 spline, all gear ratios. Revolution Gear listing, accessed 2026-09-16. ↩