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Jeep Cherokee XJ Slave Cylinder Upgrade

Converting an AX5 Transmission from Internal to External Slave Cylinder

Augustin JimenezPhotographer, Writer

If there's one thing we really dislike on early Jeep Cherokee XJ's and Wrangler YJ's, it's the dreaded internal hydraulic clutch slave cylinder/throwout bearing that likes to leak and lose pressure over time. It's a fairly common problem, and it can become the proverbial “can of worms” when it fails. If a headlight fails, it's easily removed. However, on a Jeep YJ or XJ equipped with the five-speed AX5 manual transmission, you'll have to drop the transmission to get to the clutch slave.

We advocate spending your time wisely by upgrading to a much more reliable external clutch slave. There's a good reason why Jeep switched the Wrangler and Cherokee XJ to an external clutch slave for the ’94 model year. We recently found ourselves at this very crossroad and decided to roll up our sleeves to show you exactly what's involved in the AX5 external clutch slave-cylinder swap.

For this swap, you'll need to locate a new external slave-cylinder–style AX5 bellhousing, a new front bearing retainer, front bearing retainer seal, clutch fork, new hydraulic external slave cylinder, clutch master-to-slave-cylinder hydraulic line, and of course, a throw-out bearing. Luckily, Advance Adapters and Omix-ADA have most of the parts necessary to complete this upgrade.

Finding a YJ or XJ in a boneyard is just about impossible in SoCal, so we decided to call Collins Bros. Jeep in Wylie, Texas, since it has a large collection of new and used Jeeps and Jeep parts to fix, restore, or as in our case, upgrade just about any seven-slat 4x4 under the sun. Collins Bros. Jeep was able to track down and ship a mint-looking AX5 bellhousing that would accept our external slave cylinder upgrade.

We’re going to assume that if you’re undertaking a job like this, you’re well versed in the art of dropping a transmission. It’s fairly straightforward but involves removing the drive shafts, starter, shifter, transmission and transfer case mount; jacking up the transmission and unbolting the bellhousing bolts; and then wiggling it free from the engine. It didn’t take us very long to remove ours in the driveway. Follow along as we guide you through this swap that just about any Jeep owner can do with a little elbow grease and some simple hand tools.

The first order of business after swinging the AX5 five-speed manual transmission out from under the Jeep is to remove the bellhousing from the gear case. We like using air tools whenever possible as it speeds up the install, leaving more time for sitting in the garage admiring our day’s work.

With the bellhousing removed, we unbolted the front bearing retainer. Keep in mind that once you break the seal, it will leak a bit of oil. We had the forethought to put a drain pan under it to keep driveway stains to a minimum. Be careful not to damage the gasket as it will be reused with the new bearing retainer.

We called Omix-ADA and ordered up one of its AX5 front bearing retainers. Don’t forget to pop in the input-shaft seal before bolting your new bearing retainer in place or you’ll have quite a mess on your hands.

Notice the difference between our old front bearing retainer compared to the new Omix-ADA bearing retainer. The new one has a protruding shaft that fits over the input shaft and provides a place for the throwout bearing to ride on.

We knew it would be next to impossible to find a Jeep XJ or YJ AX5 bellhousing in our local junkyards in SoCal so we called up Collins Bros. Jeep in Wiley, Texas, to track down our AX5 bellhousing. Within a few minutes there was one on its way out the door to us. Collins Bros. Jeep has been in the custom Jeep business since 1984, so you can bet they’ve got plenty of knowledge as well as parts to help get your Jeep back on the trail.

With our new front bearing retainer installed, we bolted our new (to us) AX5 bellhousing in place.

Omix-ADA sent us this new clutch fork and throwout bearing to install in our upgraded transmission. The later AX5’s used this style of clutch fork to replace our old unit that worked with a hydraulically actuated throwout bearing.

We used a little bit of bearing grease on the inside of the bearing surface to allow it to glide on the shaft with ease.

Don’t forget to add a little grease to the areas of the clutch fork that come in contact with the throwout bearing. A simple dab of grease on each side will do wonders to keep any potential chattering to a minimum.

With our transmission wrapped up and ready to be reinstalled, we filled it with the proper gear oil all the way to the fill/inspection hole. Make sure you fill it in the right place as the fill plug is located on the rear half of the housing just behind the cast iron adapter on the case.

At this point you might think you’re ready to install the transmission, and truthfully, we did too. Read on to see what we overlooked.

We didn’t realize we were missing this small clutch fork retaining clip when we first installed our transmission. Luckily, the part is quite inexpensive at 4 Wheel Parts, so we picked one up. The bad part is we had to remove everything and drop the transmission a second time. Luckily you’ll learn from our mistake and be smarter when you attempt this yourself.

Once our transmission was back in place (again), we turned our attention to the hydraulic line coming from the clutch master cylinder. We scratched our heads a few times to try to come up with a way to remove the roll pin that locks the fitting in place. We took some duct tape and a shortened nail, as well as a nut. We taped the nut down against the top of our Knipex plyers with the hole facing the ground down nail we taped to the bottom side. This was our makeshift mobile miniature press, and it worked incredibly well at pushing the roll pin out of the clutch master cylinder.

The new fitting pops right into place on the clutch master cylinder. Be sure to install the roll pin again to keep the fitting secure in its bore.

With the fitting installed, we installed the new braided-steel hydraulic line from Advance Adapters. The 90-degree bend goes toward the clutch master cylinder side.

Before installing the new external slave cylinder from Advance Adapters, we installed the bronze hydraulic supply fitting to the cylinder. It’s similar to the roll pin retainer on the clutch master cylinder.

Do not remove the plastic strap that’s holding the piston back in the bore. This piece will break off once you depress the clutch pedal the first time.

We filled the new cylinder with brake fluid and started manually pumping the piston back and forth to bleed out the air bubbles from the cylinder. Make sure the cap is off the clutch master cylinder and to have a second set of eyes watch for the air bubbles to stop. You’ll be able to feel when it’s fully bled, and then you’re ready to install it on the bellhousing.

The bellhousing has two studs on the driver side where the external slave cylinder mounts. If it ever fails in the future, we won’t have to worry about having to drop the transmission in order to row through the gears.

Don’t forget to reinstall your shifter. It would be hard to overlook since you would see a large hole where your center console.

Clutch Replacement
Normally we would recommend replacing the clutch when doing a job like this, but our stock unit looked like it was in great shape, and as it turns out, it was. The pedal effort with the new external clutch slave cylinder is much more precise and firm, and the clutch now engages smoothly, allowing us to shift our old Cherokee better than ever.