AW4 Overhaul Kit, new and ready to install. Fits the AW4. Ships fast from the USA.
A Jeep Cherokee XJ with the Aisin AW4 that flares between gears, takes a second or two to grab Drive on a cold morning, or drips fluid from the front pump and the tail housing at the same time is usually past the point where a single part will save it. This AW4 overhaul kit is built for that job on four-wheel-drive Jeeps. It is a complete set for a 4x4 unit: every friction disc, the steel plates that most budget kits leave out, a full gasket and seal set, a new filter, a front pump bushing and a new second coast brake band, so the transmission goes back together with all of its wear surfaces new at once.
The AW4 is an Aisin Warner four-speed with a separate overdrive section bolted ahead of the main gearbox. Three solenoids on the valve body steer hydraulic pressure to the overdrive clutch and brake, the forward and direct clutches, the second and first-reverse brakes and the second coast band. Each pack is a stack of lined frictions sandwiched between steels, squeezed by a rubber-sealed piston. Over the years the lining wears thin, the steels glaze or heat-spot, and the piston seals and sealing rings harden and bleed off pressure. The factory overhaul manual gives the limits: direct clutch discs are scrap below 1.84 mm thick, and the second brake pack must measure 0.62 to 1.98 mm of clearance on six-cylinder units. Once packs fall outside those numbers, new discs are the only fix. Because this kit supplies frictions and steels together, you are not trying to pair fresh lining with a heat-checked plate that will glaze it again in a few thousand miles.
The factory manual treats fluid that is dark and smells burnt as overheated, and fluid loaded with friction material or metal as a reason to check the unit's operation. A light haze of material in the pan is normal break-in, so judge the amount, not just its presence. Before you tear anything down, clear the electrical side: an open shift solenoid, a bad neutral safety switch or a damaged harness can make a healthy AW4 hold one gear or shift strangely. If the solenoids and wiring test good and the transmission still slips under load, the packs are worn. Our walkthrough on why an Aisin slips under load covers the order of checks, and a fresh AW4 solenoid kit is cheap insurance while the pan is already off.
This kit is for four-wheel-drive AW4 transmissions from 1987 through 2001. That covers the Jeep Cherokee XJ 4.0L for the full run, the Comanche 4.0L from 1990 to 1993 and the Wagoneer 4.0L from 1987 to 1993. Grand Cherokee ZJ 4.0L models from 1993 to 1998 also used the AW4, but 1994 to 1998 Grand Cherokees were built with more than one transmission, so read the transmission ID tag before you order. Two-wheel-drive units use a different extension housing, so send us your year and VIN if your Jeep is 2WD. Browse every Aisin-family part we carry on our Aisin transmission page.
Soak every new friction disc and the band in clean fluid for at least 30 minutes before assembly, as the overhaul manual requires. Lube thrust bearings and washers with petroleum jelly, then measure each pack clearance and piston stroke after it goes together instead of assuming the new parts land in range. Press the new bushing into the pump body and check it against the 38.19 mm maximum bore the manual lists. The factory fill is Mercon ATF, with Dexron II as the listed alternate, so use a current fluid rated for those specs. While the transmission is out, inspect the AW4 input drum for scoring and cracks, and add an auxiliary transmission cooler if the Jeep tows or crawls trails, since heat is what wore out the last set of frictions.
| Fits | AW4 |
| Part type | Overhaul Kit |
| Condition | New |
| 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.
It includes both the friction discs and the steel plates, plus a full gasket and seal set, a filter, a front pump bushing and the second coast brake band. Many lower-priced kits ship frictions only.
This kit is listed for 4x4 AW4 applications. Two-wheel-drive units use a different extension housing and seal, so send us your year and VIN before ordering for a 2WD Jeep.
The Jeep overhaul manual specifies Mercon automatic transmission fluid, with Dexron II allowed if Mercon is not available. Use a modern ATF that is rated for those specifications.
Yes. The factory manual calls for soaking replacement clutch and brake pack parts in transmission fluid for at least 30 minutes before installation. Dry discs can glaze on the first apply.
Inspect the drums, planetary bushings and pump gears against the manual's limits, and plan on the shift solenoids and a cooler if the Jeep has high mileage or tows. The torque converter should be flushed or replaced so old debris does not return.
