AW4 Planetary, used and ready to install. Fits the AW4. Ships fast from the USA.
When a Jeep Cherokee XJ or Comanche with the AW4 shifts fine through third but whines, slips or will not pull in fourth, the overdrive section at the front of the case is the usual suspect. This listing is a used, original Aisin overdrive planetary package: the overdrive planetary gear and ring gear with input shaft and reluctor, the overdrive support, the overdrive steels and pressure plate, the thrust bearings and washers, and the snap ring. It is meant for the rebuilder who has found a damaged overdrive gearset and wants the matched hard parts in one box.
The AW4 is a four-speed Aisin Warner unit with a separate overdrive planetary ahead of the three-speed gear train. The overdrive input shaft and planetary carrier turn as one piece. In first through third, the overdrive direct clutch and the overdrive one-way clutch tie the overdrive sun gear to the carrier, so the whole set spins as a solid 1:1 unit. In fourth, the overdrive brake holds the sun gear still and the carrier drives the ring gear faster than the input, which is the overdrive ratio. That means the pinions in this set only work hard in fourth, which is why a worn overdrive gearset often shows up as a fourth-gear-only noise or slip.
Fourth gear complaints on the AW4 are also caused by solenoid number two faults and worn overdrive brake frictions, so rule those out before you buy hard parts.
Drive the Jeep with the selector in 3 and then in D. If the noise or slip is only in fourth, the overdrive section is the place to look. Check the shift solenoids and wiring first; our Aisin slipping under load guide walks through separating electrical and clutch problems from hard-part failures. With the unit apart, the AW4 overhaul manual gives the checks: the overdrive one-way clutch must let the planetary shaft turn freely clockwise and lock counterclockwise, and the planetary gear bushing is worn out past 11.27 mm (0.4437 in) inside diameter.
The AW4 was used in the 1987-2001 Jeep Cherokee XJ, the Comanche and the XJ-based Wagoneer. This listing does not carry a year, so match parts by measurement. The gear set as described has a 26-spline shaft, a 31-tooth sun gear, a 95-tooth ring gear and 16 reluctor tabs; count yours before ordering. Aisin used a closely related overdrive section in the Toyota A340 family, so parts can look alike across units, and our AW4 vs A340E comparison explains how the two differ. If you are not sure, send us your year and VIN. You can see every AW4 part we stock on the Aisin transmission parts page.
| Fits | AW4 |
| Part type | Planetary |
| Condition | Used |
| Brand | OEM |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
The overdrive planetary gear and ring gear with shaft and reluctor, the overdrive support, overdrive steels and pressure plate, thrust bearings and washers, and the snap ring. It is used original Aisin hardware.
It is for the AW4 used in the 1987-2001 Cherokee XJ, Comanche and Wagoneer. Count the shaft splines (26), sun gear teeth (31) and ring gear teeth (95) on your unit to confirm, or send us your year and VIN.
The overdrive planetary turns as a locked unit in first through third and only drives through its pinions in fourth, so worn pinions, bearings or a bushing on this gearset are usually heard only in overdrive.
The AW4 overhaul manual specifies Mercon, with Dexron II as the alternative.
Overdrive frictions, any worn thrust bearings and races, the gaskets and seals from an overhaul kit, and the cooler or a full cooler flush so debris does not reach the new parts.
