Dana 44 Lockers and Spools

Lockers, spools and limited slips

An open differential sends power to the wheel with the least traction. Traction aids change that.

• Air and electric lockers, such as ARB's, are open on the street and lock on demand for the trail.
• Automatic lockers lock when power is applied and release in turns, with a characteristic clunk.
• Selectable lockers, like the Auburn Gear Ected Max, switch between limited slip and spool.
• Helical limited slips such as TrueTrac use gears for torque bias and operate quietly.
• Spools and mini spools permanently lock both axle shafts, which is strong but harsh on pavement.

Matching the unit to your Dana 44

Dana 44 carriers vary, so check three details first: spline count, such as 30, 33 or 35 spline, the gear ratio break, indicated as 3.73 and down or 3.92 and up, and the axle position, front or rear. Many listings are specific to the Jeep JK Rubicon, Nissan and other applications.

The carrier break matters because ring gear sizes differ across ratios, and a locker built for the wrong ratio will not fit the housing. Count spline numbers on the axle shaft or consult the manufacturer's information, and check whether the differential is a standard or Super 44, since AdvanTEK versions differ.

Choosing for your driving

A locker that engages only on demand is the most flexible for a vehicle that is also driven daily. Automatic lockers and spools are durable and simple but affect handling and tire wear. Helical limited slips are the gentle option, though they are not a true lock when one wheel is airborne.

Air lockers need a compressor and lines, and electric lockers require wiring. Consider whether the setup is for the front axle, where a locker affects steering effort on slippery surfaces, or the rear.

Installation notes

Installing a locker means setting up the ring and pinion carrier, including measuring backlash and checking pattern contact, plus fitting bearings and seals. It is exacting work, and professional installation is recommended unless you are experienced with differentials.

Use axle shafts rated for the added stress, since a locked axle puts more load on the weakest component. Follow the manufacturer's break-in and gear oil recommendations, and check local rules and the vehicle manual.

Axle shafts, ratios and setup considerations

A locker is rarely a stand-alone upgrade. Because locking sends the full torque of the engine through one axle shaft when a wheel has traction and the other does not, the shafts, U-joints and housing see greater loads. Stock shafts are a common first failure point on a heavily used vehicle, and many owners upgrade to stronger shafts when adding a locker or when stepping up to larger tires.

• Confirm the ring gear ratio and carrier break before choosing, and do not assume the existing carrier will accept the new unit
• Inspect the housing for bent tubes, worn bearing journals or cracked brackets
• Replace bearings and seals, and use the correct shims and setup tools for the ring and pinion
• For air lockers, route the air line carefully and use the recommended fittings and a protected solenoid
• Have a plan for an emergency, such as a manual release or a spare for the system

Keep driving habits in mind. A locked axle should not be used on pavement, because the tires cannot rotate at different speeds in turns. With automatic units, expect noise and some tire chirp in tight turns. Regular gear oil changes are particularly valuable, since the clutch packs or gears in these units generate wear particles.