Drop pan, replace filter and pan gasket, refill through dipstick. 30k-50k mile interval. No flush — drain-and-fill only.
AW4 service is straightforward but takes patience to refill. Procedure:
1. Warm trans by driving 5-10 minutes, then park level.
2. Drain pan: there's no drain plug from the factory — loosen the front pan bolts to break the seal, then back the others off carefully. Catch about 4-5 quarts. (You can add a drain plug aftermarket: B&M 80250 or similar.)
3. Remove the pan. The filter is held by two bolts and a snap-on connection at the valve body intake. Pull it straight down — fluid spills.
4. Replace filter (Wix 58931 or Mopar 52852913AA), new pan gasket (reusable cork or rubber from B&M or PerfBlue), and clean the pan magnet of metallic dust. A little dust is normal; chunks mean rebuild incoming.
5. Reinstall pan with gasket. Torque pan bolts to 7-8 lb-ft in crisscross pattern. Don't crush the gasket.
6. Refill: AW4 holds ~9 quarts total but only ~4-5 come out with a drain. Add 4 quarts of Dexron III/VI through the dipstick tube. Start engine, cycle through gears with brake, recheck level (cold mark first, then top up after a 15-mile drive to hot mark).
Do not power-flush. The OEM service is drain-and-fill. To get more of the old fluid out, drain-fill, drive 100 miles, drain-fill again. Three rounds essentially refreshes the fluid charge.
Fluid choice: Mopar ATF+4 (later XJs), Dexron III/Mercon (earlier), or Dexron VI (modern supersession works in both). Avoid universal multi-vehicle fluids — they often don't have the right friction modifiers for AW4 clutch packs.
| Part | Vendor | Est. price |
|---|---|---|
| Wix AW4 filter | Wix | ~$25 |
| Mopar pan gasket | Mopar | ~$18 |
| Dexron VI ATF 5qt | Valvoline/Mobil | ~$35 |
| B&M drain plug kit | B&M | ~$20 |
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.