Rear Locker for the Gladiator JT — Dana 44 Options
Difficulty 4/54–6 hrs$549–9992020-2024
The Gladiator Rubicon already comes with Tru-Lok front and rear lockers — this guide is for Sport, Willys, Overland, and Mojave owners who want locking traction without stepping into Rubicon pricing.
The rear axle on all non-Rubicon JT trims is a Dana 44 with an open differential. An open diff is fine for pavement and light gravel, but on uneven terrain — a side slope where one rear tire lifts, or a muddy wash where traction is patchy — an open diff sends power to the spinning tire instead of the tire with grip. A locker eliminates that. It mechanically (or electronically) connects both rear axle shafts so they turn together regardless of traction difference between the tires.
The ARB Air Locker ($849) is the performance choice: a pneumatic locker that engages and disengages via air pressure, giving you a true open differential on pavement and a locked rear when you activate it on the trail. ARB Air Lockers require a 12V air compressor — ARB sells a compatible twin-cylinder compressor kit ($369) that mounts under the hood. The combined cost puts the full ARB setup at roughly $1,200, but the on-demand engagement is the only design that genuinely delivers both behaviors without compromise.
The Eaton ELocker ($649) uses an electric solenoid to lock the differential on demand. It's cleaner to install than the ARB (no air lines), engages nearly as quickly, and costs less. The primary downside is that solenoid failure (which is uncommon but not unheard of) leaves you with a locked rear until you diagnose and repair it — the ARB at least fails open. The Detroit Truetrac ($549) is a helical gear limited-slip, not a true locker — it won't mechanically lock both shafts, but it biases torque to the gripping tire more aggressively than an open diff. It's the choice for owners who want improved traction without any driver activation required and don't need a fully locked differential.
Backlash and preload are pass/fail, not close-enough. The two numbers that make or break this job are pinion bearing preload and ring-and-pinion backlash (.006"–.010" on the Dana 44). Too tight and the gears run hot and howl; too loose and they clunk and wear fast. A dial indicator is not optional here — if you don't have one and can't read a contact pattern with marking compound, this is the moment to hand the diff to a shop rather than guess.
Mark the bearing caps before they come off. The caps are machined in place and are side- and orientation-specific. Swapping or flipping them changes the bore and ruins your preload. Center-punch or paint-mark them before removal.
Don't reuse the crush sleeve or old seals. If your teardown disturbs the pinion, use the new collapsible spacer and axle seals from the install kit. Reused seals weep, and a reused crush sleeve won't hold preload.
ARB fails open, ELocker fails locked. Weigh that into the choice: an ARB compressor or air-line failure leaves you with a normal open diff and a drivable truck. An ELocker solenoid stuck engaged leaves you with a locked rear until you can address it — safe to limp home slowly, but plan your exit.
Parts land at $549 (Truetrac) to roughly $1,200 (ARB with compressor). Shop labor to install a locker in the rear Dana 44 runs 4–6 hours, typically $400–700 depending on rates. The single biggest way to save money: do the locker and a regear at the same time. Both jobs require the exact same teardown — pulling the carrier, resetting backlash and preload — so combining them means paying that labor once instead of twice. If bigger tires are anywhere in your plan, read Re-gearing the Gladiator JT before you commit to a locker-only install. For a factory-locked alternative and the electronic-locker comparison, see Trail-using the Rubicon's rear locker only and Dana 44 rear locker options.
Steps
Drain the rear differential fluid; loosen the cover bolts and pull the cover, catching the remaining fluid in a drain pan.
Remove the rear axle shafts: unbolt the backing plate retainers and slide the shafts out.
Remove the differential carrier: mark the bearing caps before removing (caps are side-specific), unbolt the caps, and carefully remove the carrier from the housing.
Remove the ring gear from the old carrier and install it on the new locker differential. Torque ring gear bolts to spec in a cross pattern — ring gear bolts are typically 70–90 ft-lbs.
Install the new carrier into the housing, checking bearing preload and ring/pinion backlash with a dial indicator. Backlash on Dana 44 should be .006"–.010".
Reinstall bearing caps — torque to spec, position-specific.
For ARB: drill and tap the air fitting port in the diff housing per ARB's instructions. Route the air line through the axle housing to the solenoid.
Reinstall axle shafts and backing plates. Install new axle seals with a seal driver.
Clean the diff cover mating surface, apply RTV, and reinstall cover. Fill with gear oil (75W-140 synthetic recommended; approximately 1.5–2 quarts for Dana 44).
For ARB: mount and wire the compressor, run the air line to the locker, and test engagement before trail use.
Why it works
True locking traction on the trail eliminates the one-tire-spinning problem completely
ARB Air Locker delivers transparent on-road behavior — you'll forget it's there until you lock it
ELocker is a clean install without air lines and costs less than ARB
Significant traction upgrade for any JT trim without Rubicon's Tru-Lok system
Trade-offs
Differential work requires precision — backlash and bearing preload errors cause gear noise and premature wear
ARB setup adds compressor cost and complexity; total cost exceeds $1,200 with compressor
Full locker in the rear changes on-road handling during parking maneuvers — turning radius increases when locked
Detroit Truetrac is not a full locker; it won't match the traction of ARB or ELocker in extreme situations
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.