The JL Dana 44 axles take less fluid than the JK they replaced — about 1.5 quarts per axle — and Mopar specifies 75W-85 GL-5 gear oil, with 4 oz of friction modifier added to any Trac-Lok differential.
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.
| Part | Vendor | Est. price |
|---|---|---|
| Mopar 75W-85 GL-5 gear oil (1 quart) | Mopar | ~$14 |
| Mopar Trac-Lok friction modifier (4 oz) | Mopar | ~$12 |
| Mopar differential cover gasket / RTV | Mopar | ~$18 |
| Permatex Ultra Black RTV | Permatex | ~$12 |
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.