AX15 5-Speed Transmission Master Overhaul Kit Jeep

Crown Automotive AX15MASKIT is the master overhaul package for the Aisin AX15 five-speed manual — the box Jeep bolted behind the 4.0L inline six in the Wrangler YJ and TJ, the Cherokee XJ, and the Comanche MJ, and the same unit Dodge used behind the 3.9L in the Dakota. It bundles the bearings, synchronizer rings, seals and gaskets that a full teardown consumes, so you are not chasing five separate part numbers while the case halves sit open on the bench.

The AX15 gives you fair warning before it needs this kit. Second gear starts crunching on a cold morning because the brass synchro ring has worn past its cone clearance. The input bearing whines in neutral with the clutch out. Gear oil weeps from the front bearing retainer or the tailhousing seal and leaves a trail down the bellhousing. Once you are far enough in to split the case, you replace all of it at once — putting an old bearing back behind new synchros is how a rebuild comes apart twice.

Bench order matters on this transmission. Pull the shift tower and tailhousing first, press the countershaft and mainshaft assemblies out together, then work the mainshaft down on the press so the gear stack, blocking rings and snap rings come off in sequence. Lay them out in order. Soak the new synchro rings in gear oil, check each one seated on its cone for the correct gap before it goes on the shaft, and set mainshaft end play with the selective spacer before the case goes back together. Torque the case bolts in a cross pattern and prime the box with 3.3 quarts of the correct manual transmission fluid before it goes back in the truck.

Crown Automotive ships this as part number AX15MASKIT. The kit covers the overhaul hardware only — gears, shafts, shift forks and the case itself are inspected and reused or replaced separately.