ARB Ford 8.8" Rear Air Locker Differential - 31 Spline

Designed for compatible Ford 8.8" rear differential applications using 31-spline axle shafts. Vehicle year and model alone do not guarantee compatibility. Ford used multiple axle platforms and spline configurations across the vehicles listed below, so axle identification is required before ordering.

Fitment Notes:

• Fits compatible Ford 8.8" rear axle applications
• Requires 31-spline axle shafts
• Compatible with Ford 8.8" gear ratios when the housing and carrier configuration match
• Rear differential applications only
• Operates as an open differential when disengaged
• Provides fully locked axle operation when activated
• Requires a compatible compressed air supply
• ARB air compressor sold separately
• Not compatible with factory 28-spline axle shafts without the appropriate axle conversion
• Not intended as a universal replacement for every Ford 8.8" differential
• Verify axle identification, spline count, bearing configuration, and ring gear mounting specifications before ordering
• Professional differential installation and air system routing are recommended

Builder Note: Ford 8.8" axles are popular in Jeep swaps, rock crawlers, and custom off-road builds because of their compact size and aftermarket support. However, not every Ford 8.8" axle uses 31-spline shafts. Many Ranger and passenger vehicle applications were equipped with 28-spline shafts, while other vehicles used different axle platforms entirely. Confirm the actual axle assembly before selecting the RD81.

What does the ARB RD81 Ford 8.8" Air Locker do?

The ARB RD81 is a selectable locking differential that allows the driver to switch between open differential operation and fully locked traction. When engaged, compressed air activates the internal locking mechanism so both rear axle shafts rotate together, improving traction in difficult off-road conditions.

Will the ARB RD81 fit my Ford 8.8" axle?

The RD81 is designed for compatible Ford 8.8" rear axles using 31-spline axle shafts. Verify the installed axle model, spline count, and differential configuration before ordering because not every Ford 8.8" axle uses the same internal components.

Does the RD81 fit Ford Explorer rear axles?

Yes, the RD81 is listed for compatible Ford Explorer 8.8" rear axle applications. Confirm the axle uses 31-spline shafts and matches the required carrier configuration before ordering.

Will this Air Locker fit my Ford Ranger?

Some Ford Ranger models use 8.8" rear axles, but many have 28-spline shafts or other axle configurations. The RD81 requires 31-spline axle shafts, so verify the axle and spline count before ordering.

Does the ARB RD81 require an air compressor?

Yes. The RD81 uses compressed air to engage the differential locking mechanism. A compatible ARB air compressor and air supply system are required for operation and are sold separately.

Does the RD81 stay locked all the time?

No. When disengaged, the RD81 operates as a conventional open differential. The driver activates the locker when additional traction is needed and disengages it when normal differential action is preferred.

What gear ratios work with the ARB RD81?

The supplied specifications list compatibility with all Ford 8.8" gear ratios. The installed ring and pinion must still match the correct Ford 8.8" housing and carrier configuration.

What is the difference between an ARB Air Locker and a spool?

A spool permanently locks both axle shafts together, forcing both wheels to rotate at the same speed during all driving conditions. An ARB Air Locker provides selectable locking, allowing normal differential operation on pavement and fully locked traction when needed off-road.

Can I use the RD81 on a street-driven vehicle?

Yes. Because the RD81 operates as an open differential when disengaged, it maintains normal differential action during street driving. The locking function should be used only when additional traction is needed and in accordance with ARB's operating instructions.

Is the Ford 8.8" Air Locker a good upgrade for rock crawling?

Yes. Selectable lockers are particularly useful for rock crawling because they provide maximum traction when climbing obstacles while allowing the differential to be unlocked for easier turning and normal handling.

Does the RD81 include the activation switch and air line?

Yes. The supplied kit contents include the Air Locker differential assembly, dash activation switch, solenoid valve, air line, and bulkhead fitting. The air compressor is sold separately.

Can the RD81 be installed during a ring and pinion gear change?

Yes. Installing a new Air Locker during a gear change is a practical approach because the differential carrier is already being removed. Correct carrier bearing preload, backlash, and ring gear contact pattern must be established during installation.

Will this locker work in a custom Jeep or off-road buggy with a Ford 8.8" axle swap?

Yes, provided the swapped axle is a compatible Ford 8.8" rear differential with 31-spline shafts. The locker is selected based on the axle configuration rather than the vehicle chassis.