The Jeep came equipped with the internal slave AX-15. While the AX-15 is a stout transmission, the internal slave setup is less than ideal. Any time repairs need to be made to the slave or fittings the entire tranny has to be dropped. Having had to do this several times, it became apparent that was not in my best interest. It was time to swap to an external slave setup. All jeeps manufactured after 94' with a standard transmission came equipped with an external slave AX-15. For those of you interested the swap is fairly easy and can be done for a reasonable price.
In my case I did an entire transmission swap. I am using an external AX-15 from a 98' XJ that I had rebuilt. It came complete, meaning I had the external slave bell housing, the clutch fork and bearing retainer. If you don't already have these parts you will need to source them. Due to the differences between the Renix era (86' - 90') and newer OBDI/OBDII (91' - 00') computer systems, when performing the swap in a Renix era Jeep the clutch system for Renix era (i.e., fly wheel and CPS sensor) must be used with the newer transmission.
When Chrysler changed from the internal slave setup to the external slave, the transmission input shaft diameter was changed meaning if you are using an external slave AX-15 in an older 4.0L a new pilot bearing may be in order.
- The BA10/5 and internal slave AX-15 have a pilot bearing with an Inside Diameter (ID) of 0.5934 inches, Outside Diameter (OD) of 1.055 inches, and depth of 0.719 inches (OE part number 53009181).
- The external slave AX-15 has a pilot bearing with an ID of 0.7518 inches, OD of 1.8161 inches, and depth of 0.719 inches (OE part number 33004041). The standard pilot bearing that comes usually will not fit into the crankcase as it will have to large an OD.
Side by side of the internal vs external pilot bearing (internal on the left, external on the right).
A 72 - 73’ CJ, 350 V8 pilot bearing is recommended when swapping in an external AX-15 in an older 4.0L. It has an ID of 0.751 inches, OD of 1.056 inches, and depth of 0.88 inches (National part number PB77HD or Dorman part number 14674). For my application I went with the National bearing.
The bronze bearings are impregnated with oil, so when installing do not use grease as it will contaminate the bearing. I've read to make for an easier install the night before place the bearing in some fresh motor oil and store it in the freezer. Now I may be incorrect, but I figured if its already impregnated with oil why would I need to soak it again. And in the winter its just as likely to freeze so it should not affect the bearing in any way to freeze it without additional oil. So 24 hours later I began the install. I used a make shift install tool...an old shop broom handle cut down to size. I slowly tapped it into place, taking care to make sure it was square while inserting it.
With the pilot bearing in place I moved onto installing the Luk Heavy Duty Clutch Kit. At this point as long as the clutch kit is designed for the AX-15 it is compatible. The kit comes with an alignment tool to use when installing the friction disc to the flywheel.
Fly wheel, pilot bearing, and clutch kit in.