Change TJ differential fluid every 30,000 miles or every wet trail run — Dana 30 front takes about 1.25 quarts, Dana 35 rear takes about 1.7 quarts, Dana 44 rear takes about 2 quarts of 75W-90 synthetic gear oil.
The TJ Wrangler shipped with three axle combinations: Dana 30 front on every model, Dana 35 rear on most non-Rubicon trims, and Dana 44 rear on the Rubicon (2003–2006) and some early Sahara/65th Anniversary builds. All three use the same basic service procedure — pull the cover, drain, scrape, reseal, refill through the fill plug — and all three benefit from a 75W-90 or 75W-140 synthetic gear oil. The most common mistake is changing the rear without checking what's actually back there. A Dana 35 has a smaller, more rounded cover; the Dana 44 cover is larger with a flatter bottom edge and 10 bolts.
Capacities differ. The Dana 30 front takes roughly 1.25 quarts (1.65 quarts on 1997 models, which used a slightly different housing). The Dana 35 rear takes about 1.7 quarts. The Dana 44 Rubicon rear takes 2 quarts. Buy 3 quarts if you've got the Dana 30 + Dana 35 combination, 4 quarts if you've got the Dana 30 + Dana 44 combination, and you'll have enough to refill both with a little left over for spillage.
Fluid choice matters more than the brand. 75W-90 GL-5 synthetic is the daily-driver standard. If you tow regularly or run 33s and above with regular trail use, step up to 75W-140 synthetic — the extra viscosity protects the ring and pinion under load. Skip the cheapest conventional 80W-90 unless you're flushing fluid every 15k miles. Rubicon Tru-Lok lockers do not require friction modifier. Trac-Lok limited-slip differentials (often found in the Dana 44 rear, some Dana 35s) require 4 oz of Mopar friction modifier (P/N 4318060AB) per fill, or the clutches will chatter on turns.
Most TJ axles do not have a drain plug. You drain by removing the rear differential cover, which means you'll also be replacing or reusing the cover gasket. RTV silicone (Permatex Ultra Black) is the OEM-style seal — clean both surfaces fully, lay a 3/16" bead around the bolt circle, install the cover, and let RTV cure 30 minutes before refilling. A Lubelocker reusable gasket is the upgrade — install dry, no cure time, and reusable for the next service.
| Part | Vendor | Est. price |
|---|---|---|
| Valvoline SynPower 75W-90 (1 qt) | Valvoline | ~$12 |
| Royal Purple Max-Gear 75W-90 (1 qt) | Royal Purple | ~$16 |
| Mopar 4 oz friction modifier (Trac-Lok only) | Mopar | ~$14 |
| Lubelocker differential cover gasket | Lubelocker | ~$22 |
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.