| Engine oil & filter | 4.0: 6.0 qt (5.7 L) with filter · 5W-30 (ExtremeTerrain) · 2.5: 4.0 qt | Baseline now; then per your owner's manual | Check the oil-filter-adapter O-rings while you're under there. They're a common leak that gets blamed on the rear main.Crown MFK9 master filter kit, 1997–2001 XJ · Quadratec ↗Crown MFK8 master filter kit, 1991–96 XJ · Quadratec ↗ |
| Air filter | Panel element, 1987–2001 | Baseline now; inspect every oil change | Crown's master filter kits (MFK8 / MFK9) bundle the oil, air and fuel filters.Crown 53004383 air filter, 1987–2001 XJ 2.5/4.0 · Quadratec ↗ |
| Spark plugs & ignition | Copper plugs, 0.035 in gap (4.0) · cap, rotor and wires through 1999 · coil rail on 2000–01 | Baseline now | On 2000–01 coil-on-plug trucks, a NAXJA member notes the coil rail is expensive to replace and gets blamed for misfire codes. Rule out plugs and wiring first.OMIX 17256.06 tune-up kit, 1991–93 XJ 4.0L · Quadratec ↗OMIX 17256.07 tune-up kit, 1994–96 XJ 4.0L · Quadratec ↗Crown TK-8 tune-up kit, 1997–98 XJ 4.0L · Quadratec ↗Crown TK-50 tune-up kit, 2000–01 XJ · Quadratec ↗ |
| Coolant & thermostat | 4.0: 10.5 qt (9.9 L) per the 2001 manual quote; ExtremeTerrain lists 12 qt · IAT through 2000, HOAT for 2001 (ExtremeTerrain) | Flush and refill now | Flush completely when changing coolant types. On 2000–01 trucks, a healthy cooling system is your best protection against a cracked 0331 head.Mopar 52028186AC thermostat (fits 2001 XJ) · Quadratec ↗Crown 52027984 coolant bottle & cap, 1991–2001 XJ · Quadratec ↗OMIX 17116.53 heater return hose, 1997–2001 XJ 4.0L · Quadratec ↗ |
| Automatic transmission (AW4) | Dexron III/Mercon per the NAXJA summary (ExtremeTerrain lists ATF+4; a NAXJA reply says Chrysler approved ATF+4 for the AW4 from late 2007) · 4 qt drain-and-fill, 8 qt with filter confirm in manual | Baseline now | Do a pan drop and filter change, not a pressure flush. Check the throttle-valve cable adjustment if shifts are harsh or late.AW4 filter and pan gasket search · ExtremeTerrain ↗Crown 52077578 throttle valve cable, 1991–2001 XJ AW4 · Quadratec ↗ |
| Manual transmission | AX-15: 3.32 qt 75W-90 GL-3/GL-4 (not GL-5) · AX-5: 3.3 qt same · NV3550: 2.1 qt Mopar 04874464AA or equivalent · ExtremeTerrain lists GL-5 for the AX-15 and AX-5 confirm in manual | Baseline now | NAXJA notes some owner's manuals wrongly list GL-5 for the Aisin boxes.XJ manual transmission parts · RockAuto ↗ |
| Transfer case (NP231 / NP242) | NP231: 2.2 pt (1.0 L) · NP242: 2.85 pt (1.3 L) · Dexron III/Mercon or ATF+3/ATF+4 · ExtremeTerrain lists 1.6 qt ATF+4 for the NP231 confirm in manual | Baseline now | If it pops out of 4WD or is hard to shift back to 2WD, the case may be worn.XJ transfer case seals and parts · RockAuto ↗ |
| Front axle (Dana 30) | 2.5 pt (1.2 L) SAE 75W-90 | Baseline now | Low-pinion on 2000–01 trucks, high-pinion before that. Check the inner axle seals if the knuckles are wet with gear oil.Yukon YCGD30 Dana 30 diff cover gasket · Quadratec ↗Crown 4797769 inner axle shaft slinger, 1990–96 XJ Dana 30 · Quadratec ↗ |
| Rear axle (Dana 35 / Chrysler 8.25) | Dana 35: 3.5 pt (1.66 L) · 8.25: 4.4 pt (2.0 L) · SAE 75W-90 (75W-140 synthetic suggested for towing) · add 4 oz friction modifier with Trac-Lok | Baseline now | Read the tag. ABS trucks have the Dana 35.Yukon YCGM35 Dana 35 diff cover gasket · Quadratec ↗Eaton KC8.25-76R Chrysler 8.25 master install kit · Quadratec ↗ |
| Front axle U-joints | 297x/760 series (1996 and later; check earlier ABS/non-ABS sizes) | Inspect now; replace if notchy | Turn each front wheel to full lock and check the axle-shaft U-joints for play or rust bleeding from the caps.Spicer 5-760X 297x/760x U-joint · Quadratec ↗Crown 8126638SP heavy-duty front axle U-joint · Quadratec ↗ |
| Serpentine belt & pulleys | Belt by year and accessory layout | Baseline now | OffroadXtreme says to check pulley alignment: bent pulleys suggest an overtightened belt and tired bearings.Crown 53011035 serpentine belt, 1996–2001 XJ with A/C & P/S · Quadratec ↗Crown 53010257 serpentine belt, 1996–2000 XJ with P/S, no A/C · Quadratec ↗ |
| Electric cooling fan | Confirm it switches on at idle | Check now | Idle for 5–10 minutes and confirm the fan runs. The assemblies differ for 1987–96 and 1997–2001.Crown 52005748 electric fan assembly, 1987–96 XJ · Quadratec ↗Crown 52028337AC electric fan assembly, 1997–2001 XJ · Quadratec ↗ |
| Brake fluid & rear brakes | Brake fluid per the master-cylinder cap confirm in manual | Flush now; then every 2 years | Larger tires may need more brake-pedal effort. Rear drums on most XJs need adjusting and fresh hardware.Crown 52005350KE rear drum brake service kit · Quadratec ↗ |
| Steering box & power steering | Power-steering fluid confirm type in manual | Inspect now | Check the box for seepage, and check the unibody around the box mount for cracks.Crown J8125039 steering box seal kit, 1984–2001 XJ · Quadratec ↗Crown 52038002 power steering box, 1984–2001 XJ · Quadratec ↗ |