| Engine oil & filter | 4.0: 6 qt with filter · 2.4: 4 qt · 10W-30 or 5W-30 (ExtremeTerrain) | Haynes lists every 7,500 mi or 12 months | Drain-plug torque is 25 ft-lb for the 4.0 and 2.5 and 20 ft-lb for the 2.4 (ExtremeTerrain's factory-spec table). Look for leaks at the oil-filter adapter gasket while you're under there, because it's a known 4.0 leak.Mopar 05281090AB engine oil filter, 01–07 TJ · Quadratec ↗Crown oil filter, 91–06 2.5L/4.0L YJ & TJ · ExtremeTerrain ↗ |
| OPDA check (2005–06 4.0) | Oil pump drive / camshaft synchronizer | Now, unless there's a receipt | Quadratec recommends replacing it proactively on 2005–06 trucks with no records. Listen for the 'laughing monkey' chirp at idle.Crown 53010624AC oil pump drive assembly, 05–06 TJ 4.0L · Quadratec ↗ |
| Air filter & PCV | Engine air filter and PCV | Every 30,000 mi or 24 months (Haynes); sooner in dust | Quadratec lists aging throttle-position, crank and O2 sensors as causes of stalling and rough idle, so a fresh filter rules out the easy stuff first.TJ engine & fuel system parts · Quadratec ↗ |
| Spark plugs | ExtremeTerrain's engine tables give 27 ft-lb for the 4.0 and 2.5 and 250 in-lb for the 2.4, but its ignition table says 30 ft-lb for all engines confirm in manual | Every 30,000 mi (Haynes) | Haynes lists inspecting the plug wires, cap and rotor on 2003-and-earlier models (the 1997–99 4.0 and the 2.5 have a distributor).Crown RC12ECC spark plug, 97–06 2.5L/4.0L TJ · ExtremeTerrain ↗ |
| Coolant & radiator | ≈9 qt (2.4, 2.5), 10.5 qt (4.0), 50/50 (Quadratec chart) · coolant type: conventional vs Mopar HOAT changed around 2001 confirm in manual | Every 30,000 mi or 24 months (Haynes) | Inspect the plastic radiator end tanks for seam leaks. Quadratec says they often start around 100,000 miles.Crown 52080183 replacement radiator, 87–06 YJ/TJ · Quadratec ↗Omix cooling system kit, 00–06 4.0L TJ · ExtremeTerrain ↗ |
| Manual transmission | AX-5/AX-15: 75W-90 GL-3 or GL-4 (ExtremeTerrain), ≈3.3 qt · NV3550: Mopar manual transmission fluid, about 2 bottles (4x4xplor) · NV1500: 4.8 pints · NSG370: 3.17 pints (Quadratec chart) confirm type in manual | Change now, then every 30,000 mi | The NV3550 fill and drain plugs take a 17 mm Allen bit, and the oil-pan skid may need to come off (4x4xplor). Fine filings on the magnet are normal, but chunks are not.TJ driveline parts · Quadratec ↗ |
| Automatic transmission (30RH / 32RH / 42RLE) | 42RLE: ATF+4, ≈4 qt pan drop, 8.8 qt dry (ExtremeTerrain) · 30RH/32RH: ATF type per the dipstick/manual confirm in manual | Every 30,000 mi, or 12,000 mi in severe use (Haynes) | Change the filter with the fluid. Filter screws take 35 in-lb (30RH/32RH) or 45 in-lb (42RLE) (ExtremeTerrain's factory-spec table). Drivingline calls the 2003–06 four-speed heat-sensitive, so consider a cooler if you tow or crawl.TJ automatic transmission parts · RockAuto ↗ |
| Transfer case (NP231 / NV241OR) | NV231: ATF+3 or ATF+4, 2.2 pints · NV241OR: ATF+4, 4.2 pints (ExtremeTerrain, Quadratec charts) · fill until it runs out of the fill hole | Every 30,000 mi (Haynes) | On a TJ the skid plate has to be lowered for a proper drain (4x4xplor). Drain and fill plugs take 15–25 ft-lb (ExtremeTerrain's factory-spec table). Check the output seals and the shift-linkage bushings while you're there.Crown 53004810 shift lever bushing (NP231/NV241OR) · Quadratec ↗Crown NP231 overhaul kit, 87–06 YJ & TJ · ExtremeTerrain ↗ |
| Front & rear differentials | GL-5 80W-90 or 75W-140 synthetic · Rubicon Dana 44s: 75W-140 synthetic · +4 oz limited-slip additive for Trac-Lok (Quadratec, ExtremeTerrain) | Every 30,000 mi, and after deep water (ExtremeTerrain) | Cover bolts take 30 ft-lb (ExtremeTerrain's factory-spec table). Drivingline says to check the Dana 30's pinion seal and U-joints.Gear oil and friction modifier search · Quadratec ↗ |
| Steering & front end inspection | Track bar and bolts, ball joints, tie-rod ends, drag link, stabilizer | Now, and after any lift or hard trail day | Torque the track-bar bolts to spec first. Off Road Xtreme says a loose lower bolt is the most common cause of death wobble.Ball joint, drag link sleeve and tie-rod end kit, 97–06 TJ · ExtremeTerrain ↗ |
| Brake & clutch fluid | DOT 3 (ExtremeTerrain) | About every two years | The TJ's external clutch slave shares brake fluid. Flush both.TJ steering & brakes parts · Quadratec ↗ |
| Chassis grease & U-joints | Lubricate chassis components (Haynes) | Every 7,500 mi or 12 months (Haynes) | Grease the steering joints and driveshaft U-joints, and look over the control-arm bushings.TJ driveline (U-joints, driveshafts) · Quadratec ↗ |
| Frame & floor rust inspection | Rails, rear lower control-arm brackets, transfer-case crossmember, body mounts, footwells | Now, then every winter | Quadratec warns rust at the rear lower arm brackets can cause structural failure. Clean and coat the frame inside and out before it gets there.Rust Buster rear trailing arm mounts section, 97–06 TJ · Quadratec ↗ |