A rear locker transforms how the JT handles technical terrain. The Rubicon trim comes factory-equipped with Trac-Lok (limited slip) and an optional electronic front locker — but the Sport and Willys trims get open differentials that leave you spinning one tire when traction is unequal. A locker fixes that.
The Gladiator JT's rear axle is a Dana 44 on all trims — the same core housing as the JL Wrangler rear, which means aftermarket locker support is broad. What differentiates the JT is the rear leaf spring suspension and the longer wheelbase, which changes the effective traction demand on the rear axle during articulation. When the JT's rear axle droops significantly on uneven terrain, an open diff sends power to the wheel in the air. A locker sends it equally to both — the wheel with grip does the work.
**Locker types: what they are and what they aren't**
An **automatic locker** (Detroit Locker, True-Trac variant) locks mechanically under torque and unlocks during cornering. It's always active, requires no driver input, and costs the least. The trade-off: on-road behavior is altered. The rear end "bumps" slightly in tight turns as the locker unlocks and relocks. Fine for rigs that primarily trail-drive; noticeable in street daily drivers.
A **selectable locker** (ARB Air Locker, Eaton ELocker, Yukon Zip Locker) locks on demand via a driver-controlled switch. In unlocked mode, the differential behaves normally — open (Sport/Willys) or limited-slip (Rubicon). Engage it when you need it. This is the right choice for a JT that divides time between street driving and trail use.
**ARB Air Locker** ($849): The industry benchmark for selectable lockers. Pneumatically actuated via an air compressor (the ARB twin-motor compressor, ~$350 separately). Rock-solid engagement, well-documented install procedure, broad JT fitment support. Requires routing an air line from the compressor to the axle — adds installation complexity but the reliability record is exceptional. If you're installing a front locker too, one ARB compressor handles both.
**Eaton ELocker** ($749): Electrically actuated — a 12V solenoid engages the locker on demand, no compressor required. Wiring is more straightforward than ARB pneumatic plumbing. The engagement is slightly slower than the ARB (takes a half-second to lock fully), which is irrelevant in real use. A strong choice for JT owners who want selectable without dealing with air line routing.
**Detroit Locker** ($499): Automatic, always-engaged under power. Zero installation electronics required — it's a drop-in carrier replacement. Lowest cost, highest off-road traction output. The right call for a dedicated trail rig; less ideal for anything driven on-road daily.
Differential locker installation involves removing the rear axle from the vehicle, disassembling the differential carrier, pressing out the old carrier bearings, installing the locker assembly into the carrier, and reassembling with careful attention to ring gear backlash and bearing preload. This is a precision job — bearing preload measured in inch-lbs and backlash measured in thousandths of an inch. The cost of getting it wrong is a destroyed ring-and-pinion.
For most JT owners, the right call is finding a drivetrain shop familiar with Dana 44 work and paying the labor. The install itself takes an experienced mechanic 4–5 hours. A first-timer without a ring gear spreader and dial indicator adds significant risk and time.
**If you're doing it yourself:**
1. Drain differential fluid and remove the cover.
2. Mark the caps before removal — they're machined as a matched set to the housing.
3. Use a ring gear spreader to spread the housing enough to remove the carrier assembly. Forcing it without a spreader damages the housing.
4. Press out the carrier side bearings using a bearing press — not a C-clamp, not hammer and drift.
5. Install the locker assembly per the manufacturer's instructions. ARB and Eaton both include detailed installation guides.
6. Set ring gear backlash (spec for Dana 44: 0.005"–0.008"). Use shims to adjust.
7. Set carrier bearing preload — typically 25–30 in-lbs rotating torque over the rolling friction.
8. Reinstall caps to original orientation and torque to spec (60–80 ft-lbs depending on year).
9. Reinstall the axle, refill with differential fluid (75W-140 synthetic for a locker, not 80W-90), and test engagement in a safe area before hitting the trail.
Detroit Locker (automatic, no electronics): ~$499. Parts-only — add shop labor if not self-installing.
Eaton ELocker: ~$749. Add wiring harness and switch (~$50 separately) and a few hours of labor for the wiring run.
ARB Air Locker: ~$849 for the locker + ~$350 for the twin motor compressor. All-in cost including install labor runs $1,400–1,800 at a reputable shop.
Shop install labor (any locker type): $400–600. Differential work is the one area where cutting corners costs more in the long run.
| Part | Vendor | Est. price |
|---|---|---|
| ARB Air Locker for Jeep Gladiator JT Rear Dana 44 | ARB | ~$849 |
| Eaton ELocker for JT Rear Dana 44 | Eaton | ~$749 |
| Detroit Locker for Dana 44 (compatible) | Eaton | ~$499 |
| Yukon Gear Zip Locker for Dana 44 | Yukon Gear | ~$599 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.