Every XJ has two differentials — front and rear — that need fresh gear oil every 30,000 miles or immediately after any water crossing deep enough to touch the axle housings. Neither has a drain plug. You pull the cover, drain it into a pan, inspect the gears while you're in there, reseal with RTV, and fill through the plug hole. Plan two to three hours if you're doing both at once.
The XJ Cherokee ran two different rear axles depending on year and option package: the Dana 35C and the stronger Chrysler 8.25. The front is always a Dana 30. Knowing which rear axle you have before you start matters — the 8.25 holds more fluid and the fill plug is different. Both rear axles share the same fluid spec and the same cover-removal procedure, so most of these steps apply to either.
**Identifying your rear axle:** Look for a metal tag riveted to one of the axle tubes, usually on the passenger side near the differential. The tag will list the axle model and ratio. If the tag is missing, count the bolts on the rear differential cover: both axles use 10 bolts on a roughly similar cover, but the 8.25 cover has a slight pumpkin shape with a notch at the bottom, while the Dana 35 cover is rounder. When in doubt, your VIN's build sheet (available through NAXJA or moparinfo.com) will confirm it.
**Capacities at a glance:**
| Axle | Position | Capacity |
|---|---|---|
| Dana 30 | Front | ~1.2 qt (1.1 L) |
| Dana 35C | Rear | ~1.7 qt (1.6 L) |
| Chrysler 8.25 | Rear | ~2.1 qt (2.0 L) |
**Trac-Lok:** Some 8.25 rear axles were equipped with Trac-Lok limited slip. If yours has it, add 4 oz of friction modifier to the rear differential fluid — without it, the clutch pack chatters during slow turns. Most XJs did not come with Trac-Lok from the factory. To confirm: raise the rear off the ground and turn one wheel by hand. If the opposite wheel turns the same direction, you have a limited slip. If it turns the opposite direction, it's an open diff.
**Change interval:** Every 30,000 miles under normal conditions. After any trail run where water crossed the axle housings, drain and refill within a day or two — water emulsifies gear oil into a grayish-brown sludge that strips lubrication quickly and accelerates ring and pinion wear.
| Part | Vendor | Est. price |
|---|---|---|
| 75W-90 GL-5 Gear Oil (3 qt — covers both diffs) | Red Line | ~$36 |
| 80W-90 GL-5 Gear Oil (3 qt — budget option) | Valvoline, Royal Purple, any major brand | ~$18 |
| Friction Modifier — Trac-Lok equipped only (4 oz) | Mopar | ~$8 |
| Permatex Ultra Black RTV Gasket Maker | Permatex | ~$10 |
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.