AW4 Auto Transmission Overview and Durability
Aisin-Warner 4-speed (Toyota A340 family), electronically controlled, lockup converter. Bulletproof when kept cool and fed clean fluid. The right transmission for an XJ.
The AW4 is a 4-speed automatic built by Aisin-Warner — essentially the same hardware as the Toyota A340/A341 found in Supras, Cressidas, IFS Tacomas, and Lexus LS400s. Used in XJs from 1987-2001 behind the 4.0L (some 2.5L apps too).
Ratios:
- 1st: 2.804
- 2nd: 1.531
- 3rd: 1.000
- 4th: 0.753 (overdrive)
- Reverse: 2.393
The transmission is electronically shifted via a TCU (separate from the engine PCM until 1996, then integrated). Lockup torque converter engages in 3rd and 4th. Power Mode and Comfort Mode buttons alter shift schedule.
Durability: legendary. The case is iron, the planetary gears are oversized, the friction packs are robust. 250k+ mile examples are common with nothing more than fluid changes. The most frequent failure modes are heat-induced (burned 3-4 clutch pack from towing without aux cooler) or TCU/solenoid (electrical, not mechanical).
Maintenance: ATF + filter every 30-50k miles. Use Dexron III (or Dexron VI as supersession). Mopar +4 is also commonly recommended for the later trucks. NEVER use a flush machine — drain-and-fill only.
Known issues:
- Solenoid resistance should be 11-15 ohms hot. Drifts out of spec, causes harsh shifts.
- TCU itself rarely fails; the solenoid pack inside the valve body fails more often.
- Lockup shudder when fluid is old.
- A leaky front pump seal at 200k+ miles.
When to swap: only if you want manual control or massively higher torque capacity. For 99% of XJ builds, keep the AW4 and add a cooler.
Why it works
- bulletproof
- shares parts with Toyota
- good ratios for 4.0L
Trade-offs
- no manual control
- TCU electrical quirks
Tools required
- transmission dipstick
- flashlight
Sources
Related
- AX-15 Manual Transmission Overview
- AW4 vs Alternatives (When to Swap)
- All Jeep Cherokee XJ guides & tools
- Browse the full DIY database
Written and maintained by an AZ wheeler and driveway wrencher. How we source guides. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.