Differential Fluid Change — Dana 44 Front and Rear

The JL inherited the Dana 44 designation but the axles themselves are new — they're called AdvanTEK and they hold noticeably less fluid than the JK Dana 44. Plan on 1.4 to 1.6 quarts per axle (front and rear), not the 2.3 quarts you'd put in a JK. Overfilling is a real risk because the fill plug is positioned higher than the actual fill line on some axle covers — fluid coming out of the hole doesn't always mean the diff is full to spec. Trust the manual capacity and measure what goes in.

Mopar's recommended fluid is 75W-85 GL-5 hypoid gear oil (part #68218057AA). The owner's manual for some JL configurations also lists 75W-140 for severe trailer-towing use. For 99% of owners running street and trail, 75W-85 is correct. Any name-brand GL-5 in that viscosity works — Mobil 1 Synthetic 75W-90 is a common and acceptable substitute, despite being a half-step heavier.

Trac-Lok limited-slip rear axles (standard on Sahara, optional on Sport S) require friction modifier. The Mopar additive is part #04318060AC, 4 ounces per axle. Without it, the clutches will chatter on slow corners — you'll hear it as a series of clunks from the rear end when turning. Lockers (Rubicon front and rear) do not need friction modifier.

The first fluid change matters most. Factory fill carries break-in metal from the ring and pinion. Mopar's service interval is 67,500 miles for normal use, 30,000 for severe service — but pulling the cover at 5,000–7,500 miles after delivery and replacing the fluid is cheap insurance. After the first change, every 30,000 miles is reasonable; sooner if you submerge the axles or wheel in mud often.

There is no drain plug on the AdvanTEK covers — you remove the cover to drain. That makes this a bigger job than it sounds, because you'll need to clean the cover, the magnet, and the housing mating surface, then re-seal with RTV. Bolts are 13mm, torque to 30 ft-lb in a cross pattern. Wait at least an hour for the RTV to skin before adding fluid.

Steps

1. Park on level ground. Warm the axles by driving a few miles — warm fluid drains cleaner.
2. Place a wide drain pan under the diff cover. Remove the fill plug FIRST (1/2" ratchet drive). If it won't break loose, stop — you don't want to drain a diff you can't refill.
3. Crack the bottom cover bolts, then loosen the upper bolts. Leave the top two snug and let the cover hang open at the bottom to drain.
4. Once drained, remove all bolts and pull the cover. Inspect the magnet — fine fuzz is normal, chunks or chips are not.
5. Clean the cover, magnet, and housing mating surface with brake cleaner. Both surfaces must be bare metal and dry.
6. Apply a 1/8" bead of Ultra Black RTV around the cover, encircling each bolt hole. Install cover and torque bolts to 30 ft-lb in a cross pattern.
7. Wait one hour for RTV to set.
8. Use a fluid pump to add 1.5 quarts of 75W-85 GL-5 through the fill hole. Add 4 oz friction modifier first if Trac-Lok.
9. Reinstall fill plug, torque to 25 ft-lb. Clean any drips.

Why it works

• Cheap insurance against ring-and-pinion wear
• Catches early bearing failure (metal on magnet)
• 30,000-mile interval is reasonable for a trail-driven JL
• Lockers don't need friction modifier — more straightforward than older Trac-Lok-only platforms

Trade-offs

• No drain plug — full cover removal required
• RTV cure time blocks the job for an hour
• Fill plug position can fool you into overfilling — measure what goes in
• Trac-Lok chatter is the symptom of missed friction modifier, and the fix is another fluid change

Tools required

• 3/8 ratchet
• 13mm socket
• fluid pump
• drain pan
• torque wrench
• RTV gasket maker

Parts

Sources

• Motobilt — Jeep Wrangler Differential Fluid Capacity Chart
• JL Wrangler Forums — Rubicon Rear Differential Gear Oil Capacity Surprise
• JL Wrangler Forums — Differential Fluid Discussion

Related

• All Jeep Wrangler JL guides & tools
• Browse the full DIY database

Written and maintained by an AZ wheeler and driveway wrencher. How we source guides. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.