Differential Fluid Change — Jeep Gladiator JT Front and Rear Dana 44
Difficulty 2/51.5–2.5 hrs$40–952020-2024
The JT Gladiator's front and rear Dana 44 axles hold approximately 1.6 quarts of fluid each. Rubicon trims with the factory locker require a friction modifier additive — without it, the Tru-Lok locker chatters and shudders during low-speed turns.
Jeep specifies 75W-140 full synthetic gear oil for the JT's Dana 44 axles. Change interval is 30,000 miles under normal use — or after every water crossing where the axles were submerged. Water contamination in differential fluid turns it milky gray and looks nothing like fresh gear oil. If you've wheeled through a significant water crossing, check the axle fluid within a week. A half-pint of water in a differential will destroy bearings over 5,000–10,000 miles.
Rubicon locker note: The Tru-Lok locker in the Rubicon front and rear axles requires Mopar friction modifier additive in the gear oil — or equivalent (Loctite 504821). Without it, the clutch packs chatter during parking-lot turns. This is normal behavior initially after an oil change without additive, but persistent chatter means the clutch pack surfaces are being worn prematurely. Use the additive.
Non-Rubicon JT trims (Sport, Overland, Mojave): standard 75W-140 synthetic, no additive needed.
Dana 44 fill capacity: Front approximately 1.6 quarts, rear approximately 1.75 quarts. Fill to overflow — don't estimate.
Synthetic vs. conventional: Use full synthetic 75W-140 only. The Dana 44 in the JT runs at higher loads and temperatures than older axle designs, and conventional gear oil won't keep up over a 30,000-mile interval.
Rubicon front locker vent: The Rubicon's front axle has an air locker connection — a small airline fitting on the axle housing. Don't confuse it for a fill plug. It's usually smaller and has a fitting, not a square drive.
Aftermarket locker service (ELocker, air locker): If you've added an aftermarket locker, check the manufacturer's fluid specification. Some aftermarket lockers specify a different viscosity or prohibit friction modifiers.
The axles under a JT are badged Dana 44, but they are the AdvanTEK generation: M210 front, M220 rear. The M220 runs a 220mm ring gear versus the legacy Dana 44's 216mm, with its own carrier, bearings, cover, and bolt pattern. Practical consequence for a fluid change: parts listings that say "Dana 44" without specifying JL/JT or M210/M220 are usually for the legacy axle and will not fit. This is the same trap covered in the rear locker guide — anything internal to these axles must be catalogued for the JL/JT application specifically. Fluid spec is unaffected (75W-140 synthetic either way), but covers, gaskets, and hardware are not interchangeable with a TJ/JK-era 44.
The drained fluid is a free axle inspection — look before you dump the pan:
Dark amber to brown, slight metallic sheen on the magnet: normal wear. The cover magnet collecting fine gray paste is expected; that is what it is there for.
Milky, gray, or coffee-with-cream: water. Change the fluid, drive a week, change it again. If the second drain is milky too, hunt for the entry point — most often the axle vent hose has cracked or popped off its fitting on the housing. Extend the vents if you cross water regularly.
Glitter, flakes, or chunks on the magnet: bearing or gear damage. Do not refill and hope. Pull the cover, photograph the ring gear wear pattern, and diagnose before the carrier bearing finishes letting go on a trail.
Burnt smell with black fluid: overheated — common after heavy towing or long sand running. Shorten the interval to 15,000 miles if this is your use pattern.
75W-140 synthetic gear oil: ~$16–20 per quart. You'll use 3.5 quarts for both axles (front + rear). Two quarts of Mopar or Royal Purple covers it if each axle is slightly under 1.75 quarts.
Friction modifier (Rubicon only): ~$12–15 per bottle. One bottle per differential (front and rear each get one bottle).
Sealant: one tube of Permatex Ultra Grey or Mopar RTV (~$10) covers both axles with plenty left over. Legacy Dana 44 cut gaskets sold by parts counters do not match the M210/M220 cover bolt pattern — skip them and use RTV like the factory did.
Total per axle: ~$35–45. Both axles: ~$65–90. A shop charges $80–120 per axle for differential fluid service on a JT. Do both at home in an afternoon.
Steps
Warm the differential slightly — 10–15 minutes of driving — to thin the old gear oil for more manageable draining. Hot gear oil is dangerous; warm is the target.
Jack the vehicle and support it on jack stands to level the axle. Differential drain and fill is more manageable on level ground.
Position a 2-gallon drain pan under the front differential. Remove the front differential cover bolts. Start from the bottom and work up — when you break the cover loose, old fluid will run out.
Allow the old fluid to drain completely. Inspect the drained fluid: dark and slightly metallic is normal. Milky or gray means water ingestion. Metallic chunks mean bearing damage — stop and investigate before refilling.
Clean the differential cover mating surface with a gasket scraper and brake cleaner. The factory seal is RTV, not a cut gasket — scrape every trace of the old bead off both the cover and the housing face. Any leftover ridge becomes a leak path.
Inspect the ring and pinion gears and carrier bearings through the open cover. Look for scoring, pitting, or unusual wear on the gear teeth. Everything should look uniform — no bright patches on only one section of a tooth.
Lay a 3/16" bead of RTV (Permatex Ultra Grey or Mopar RTV) around the cover flange, circling inside each bolt hole. Install the cover and torque the bolts to spec in a crosshatch pattern. Then wait — RTV needs about an hour of set time before it will hold gear oil. Filling immediately is the classic cause of the slow weep that shows up a week later.
Locate the fill plug on the side of the differential housing (not the cover — a separate smaller plug on the housing, typically 3/8-inch square drive). Remove it.
After the RTV has set, use a fluid pump or squeeze bottle to pump fresh 75W-140 gear oil into the fill port until fluid begins to run out the hole — this is the correct fill level indicator (full when it's running out). For Rubicon: add the friction modifier first, then fill with gear oil to overflow.
Reinstall the fill plug. Torque to 30 ft-lbs.
Repeat for the rear differential.
Lower the vehicle, take a short drive, and re-check both fill plugs for leaks.
Tools required
socket set (3/8 drive)
drain pan (2 gallon)
3/8 ratchet and extension
fluid pump or squeeze bottle
rags
gasket scraper if reusing cover
Parts
Part
Vendor
Est. price
Mopar Gear and Axle Lubricant 75W-140 (Rubicon limited-slip additive included)
Mopar
~$18
Royal Purple Max-Gear 75W-140 Synthetic Gear Oil
Royal Purple
~$16
Mopar Friction Modifier for Limited-Slip Differential
Mopar
~$12
Permatex Ultra Grey RTV Gasket Maker (M210/M220 covers seal with RTV, not a cut gasket)
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.