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Mean Max 05-14-2010 10:09 PM

Major Repair - AX-15 rebuild

Okay kids, hang on for a while because this could be a bumpy ride!

I am just starting an AX-15 rebuild on an old neglected AX-15 that has around 200,000 miles on it and has been sitting outside for a few years. This is about as "worst case scenario" as you can get. It was the OE transmission for the '92 YJ owned by JF member Jerry "JeepsOLot" until the syncros wore out & he replaced it a couple of years ago. It sat outside of his house for a long time until he gave it me, and then it sat outside at my house for over a year completely exposed to all weather conditions.

Jerry was kind enough to be my assistant on this project. We'll start with dis-assembly of this beauty.

Here it is as it sat outside without the shift tower or bellhousing on it.

On the passenger side, a 27MM is used to remove the reverse light switch.

On the top of the rear case where the shift tower bolts on, a 24MM removes the 2 shift detents that provide the spring loaded action that keeps the shifter centered.

Remove the 12MM bolt that attaches the shift arm to the pivot rod.

From the rear, remove the 10MM allen head plug and slide the pivot rod out. See the hole in the end of the pivot rod? This must face the allen head plug. If installed backward, there will be no hole & the pivot rod will bottom out on the plug resulting in having no 1st, 3rd, or 5th gears.

Here you can see that the bolt for the shift arm is a shouldered bolt & the hole for it is bored to accept the shoulder. Make sure that the threaded hole is oriented properly during assembly.

Use a Torx 40 to remove the plug, spring, and ball for the 5th gear shift detent. It's located on the right side of the rear case, just above & rearward of the reverse light switch.

A 14MM socket is used to remove the 10 bolts from the rear case. These bolts pass through the intermediate plate & thread into the front case.

Looking at the rear, I started removing the bolts in a clockwise pattern. You can see that they are all the same length, except for the 2 longer ones on the right side that are located above & below the 5th gear detent. The 1 with the wire clamp is the top one (of those 2) and holds the reverse light wiring.

Use a large prybar between the lugs on the case & intermediate plate to pry them apart.

Max :cheers2:

Mean Max 05-14-2010 10:10 PM

Before removing the rear case, pull the pivot rod out.

Then pull the shift arm out through the shift tower opening.

A few taps with a plastic hammer breaks the seal on the rear case.

Not very pretty, huh? It's actually better than I expected!

Remove the 8 front bearing retainer plate bolts with a 12MM socket. They are all the same length.

Note that this AX-15 has a 0.750 inch input shaft, and it has an internal slave style bearing retainer plate.

Remove the input shaft bearing snap ring.

Remove the cluster gear shaft bearing snap ring.

With those 2 snap rings off, you're ready to pull the front case off.


As with the rear case, use a large prybar between the lugs on the case & intermediate plate.

Having an assistant hold the transmission upright with the input shaft resting on a non-marring (wood?) surface makes maneuvering the front case off easier.

Lay the transmission upside down, with the cluster shaft facing up. Install some bolts, nuts, & washers from the hardware store in the 2 bottom holes of the intermediate plate.

Now lock the intermediate plate into a bench vise by the previously installed bolts. This will prevent damage to the sealing surfaces of the intermediate plate.

Max :cheers2:

Mean Max 05-14-2010 10:10 PM

Here is a detailed pic of the passenger side, with the transmission oriented as it would be normally. On the rear side of the intermediate plate, 5th gear resides all alone, accompanied by the shifter assembly.

And the driver's side. The mainshaft is on top, the cluster gear shaft on the bottom. Looking at the mainshaft, the helical cut gear closest to the intermediate plate is 1st gear, the next helical cut gear to the left is 3rd, then 2nd is the next helical cut gear, and finally 4th is the last one on the left.

Use a 10MM to remove the bolt from the 5th gear shift fork.

Two equal length screwdrivers should be used with a hammer to pop off the snap ring from the 5th gear syncro hub.

A standard puller will pull the first part of the assembly off.

After the puller gets it loose, remove the engagement gear & syncro ring.

Now the hub sleeve & shift fork can be removed.

The hub & cluster shaft gear for 5th gear will slide off.

Inside the hub is a 2 part "clamshell" style caged needle bearing. This one is trashed because the needles are falling out of the cages.

Behind the cluster gear is a thrust washer. It has a centering ball cutout that coincides with a centering ball that rides in the shaft. DO NOT LOSE THIS BALL!!!

Remove the ball with a magnet, and notice that the thrust washer has a chamfered side that faces the bearing in the intermediate plate.

Use a 12MM to remove the 4 bolts that attach the retaing plate to the intermediate plate. This will expose the snap rings for the mainshaft & cluster gear shaft bearings, and allow the reverse idler shaft to be removed.

The plate will slide right over 5th gear on the output/mainshaft without any problem.

Here you can see the reverse idler shaft, and the cutout in the shaft where the plate locks it in place.

Max :cheers2:

Mean Max 05-14-2010 10:11 PM

Pull the reverse idler shaft out & the counter gear off.

This tab rides in the groove on the counter gear. The shifter slides the counter gear forward to engage reverse, and rearward to disengage reverse.

The arm goes under the cluster gear & has a forked end that engages a pivot point. The arm above it attaches to the shift rail. The angle "wing" at the shift rail is what pushes the reverse light switch.

Remove the 2 bolts holding the pivot point on with a 12MM socket.

I removed only the bracket. The arm was left on the shaft rail.

Using a 10MM socket I removed the bolts from the 1st/2nd gear shift fork, and the 3rd/4th gear shift fork.

The snap ring on the cluster gear shaft bearing can be removed using snap ring pliers.

And also on the mainshaft bearing too.

A few light taps with a plastic hammer on the rear of the mainshaft & cluster gear shaft will move them forward enough to separate the shafts from each other. I let the cluster gear shaft hang down for a second while I handle the input shaft & mainshaft.

As soon as the two shafts separate, the input shaft can be removed. It can easily fall off the mainshaft, so do it quickly!

Now the mainshaft can be removed.

Then the cluster shaft can come out.

Here you can see that we never had to remove any shift rails from the intermediate plate. This makes things a LOT quicker!

Here you can see that we have completely broken down the transmission internals into sections. It's really not as bad as you might have thought, it makes for a great project!

Max :cheers2:

Mean Max 05-14-2010 10:11 PM

I sure hope this helps someone out with their rebuild.

Now I'm just waiting on the rebuild kit to show up so we can get busy pressing the gears off of the shaft & replacing the syncros!

Meanwhile, I can get the cases cleaned up & ready to reassemble!

Max :cheers2:

Mean Max 07-12-2010 07:44 AM

Okay, so that particular AX-15 rebuild is a little stalled, because another one got shoved ahead of it. So I will continue this thread by picking up where I left off. The only difference is that it's actually a different AX-15. We left off after removing the cases & pulling all the shafts from the intermediate plate.

First we will replace the input shaft main bearing, 4th gear syncro, and the bearing that allows the input shaft to spin on the main shaft. Start by removing the snap ring from the input shaft main bearing.

Then select a bearing splitter to press the bearing off.

Press the bearing off the input shaft.

Once the bearing is loose, replace it with the new one & make sure that your snap ring groove is properly oriented. This groove is for the snap ring behind the front bearing retainer plate.

When pressing the new bearing on, I use a piece of wood to avoid damage to the area where the 4th gear syncro interacts with the input shaft.

Make sure the bearing is fully seated & there is sufficient room for the snap ring.

Install the snap ring & make sure it is fully seated on the shaft.

Select the correct syncro and bearing for the input shaft & set it all aside. The input shaft is done & ready to reinstall into the case later on.

Max :cheers2:

Mean Max 07-12-2010 08:25 AM

Now on to the main shaft. Start by removing the snap rings located at either end of the shaft assembly. The one at the output shaft end is the 5th gear snap ring, and the one on the input shaft is for the 3rd & 4th gear hub.

Use two screwdrivers of equal length to remove the snap ring located near 5th gear.

Snap ring pliers will be required for the one at the 3rd & 4th gear hub.

Here you can see why the snap rings require different methods for removal. The 5th gear clip (left) doesn't completely encircle the shaft, while the 3rd & 4th gear hub snap ring does.

5th gear should slide off of the shaft fairly easily.

Note that the 5th gear is not the same on either side. The side where the snap ring is located rides very close to the shaft, and the backside does not.

Now the bearing on the output shaft end can be pressed off. Use a bearing splitter behind 1st gear to press the bearing off.

Here is the bearing right after it popped loose. You can now remove the pieces as described below.

Remove the bearing.

Remove the thrust washer.

Remove 1st gear.

Remove the 1st gear caged needle bearing.

Remove the nylon 1st gear bearing spacer.

Remove the 1st gear syncro.

Remove the alignment pin for the previously removed 1st gear thrust washer. DO NOT LOSE THIS PIN!

Here are the parts that we have removed so far, in the correct order.

Max :cheers2:

rustywrangler 07-12-2010 08:34 AM


All other posts in here will be deleted besides Mean Max's

Mean Max 07-12-2010 12:08 PM

Now remove the snap ring that secures the 1st & 2nd gear shift hub assembly on the main shaft.

Use a bearing splitter under 2nd gear to push the hub assembly off in your shop press.

Once the hub is clear of the splines, you can remove it by hand.

Now you can remove 2nd gear & it's syncro.

Here you can see that 2nd gear also has a caged needle bearing just like 1st gear has.

Here is a shot of all the parts that have been removed from the main shaft, and the were all removed from the output shaft end. All that remains on the shaft is 3rd gear and the hub assembly for 3rd & 4th gear. These last items will be pressed off of the input shaft end of the main shaft.

Remove the snap ring from the input shaft end that secures the 3rd & 4th gear shift hub assembly.

Notice the orientation of the shift collar on the hub assembly. It must be reassembled this way. One side is chamfered while the other is not.

Place the bearing splitter under 3rd gear & press everything off of the input shaft end.

This completes the entire main shaft disassembly. Take note of the orientation of the shift collar, the 3rd gear caged needle bearing, and the flange on the main shaft itself.

As soon as I have some more time to update this thread, we'll start on reassembly! :thumbsup:

Max :cheers2:

sequel 07-12-2010 03:24 PM

Good stuff.

Man...this does not look safe....

Mean Max 07-13-2010 07:42 PM

Start reassembly by fitting third gear onto the input shaft end of the main shaft with a new caged needle bearing & a new syncro.

Then install the 3rd & 4th gear shift hub & press it on.

Press it on far enough to seat the snap ring onto the shaft.

Make sure that the 3 cutouts on the syncro remains aligned with the 3 lockout tabs between the hub & shift collar.

By the time you've made it this far, you'll understand that you need to reassemble the shaft components in the order you pulled them off, except that you'll be using new bearings & syncros.

Remember that there is a snap ring after the 1st& 2nd gear hub assembly, so these items must be installed before the rear main bearing & 5th gear.

Once reassembled, the main shaft & the counter shaft can be reinstalled into the intermediate plate. They must be installed simultaneously in order to mesh the gears properly. This is an old disassembly picture, but it accurately depicts what you need to do. Note that the shift forks must be engaged into the shift collars as the shafts are being fitted.

The input shaft also must be fitted as the main shaft & counter shaft are inserted into the intermediate plate & the shafts are meshed.

Install & tighten the shift fork bolts that secure them to the rails.

Again, these are disassembly pics but they depict the snap rings that must be installed on the main shaft & counter shaft bearings.

Install the reverse idle gear shaft & idler gear.

Install the rear bearing retainer plate, which also secures the reverse gear idler shaft.

Max :cheers2:

Mean Max 07-13-2010 08:21 PM

Now your transmission should be fully complete on the front side of the intermediate plate. It should look like this.

Install the locating ball into the counter shaft on the rear side of the intermediate plate.

Line up the cutout in the thrust washer with the previously inserted locating ball on the counter shaft.

The thrust washer should look like this when it is bottomed out on the bearing.

Now put the 5th gear counter shaft gear/hub assembly onto the counter shaft.

This assembly uses a 2-piece caged needle bearing. The bearing halves can be installed individually.

Install the 5th gear syncro, making sure that the cutouts remain aligned with the lockout tabs.

This is where a helper comes in handy. Using feeler gauges removed from a feeler gauge set, your helper can hold the syncro in place while the 5th gear counter shaft gear can be installed.

I use a large socket to tap the gear onto the shaft while my helper keeps the syncro seated.

Once the gear is seated, install the snap ring.

Now slide the 5th gear rail back just far enough to install the 5th gear shift fork.

Line up the rail & slide it through the shift fork. Then install & tighten the bolt that secures the shift fork to the rail.

This completes the assembly of the internal components that are attached to the intermediate plate.

Max :cheers2:

Mean Max 07-13-2010 09:02 PM

I place the clean front case section on a milk crate & center the input shaft hole on a hole in the crate.

Now I install the aviation sealer (I love that stuff!) on the sealing surface of the front case half.

Now you can drop the assembled intermediate plate into the front case half.

Prep the rear case half by installing a new output shaft seal.

Apply sealer and install the plastic oil diverter in the recess under the output shaft hole.

Install the rear case half, put the bolts in place & tighten them up.

Put the transmission on the bench & install the snap rings on the input shaft & counter shaft.

Install the shift arm & rod, then the 10MM allen cap.

Install the shifter detents.

Install the 5th gear detent ball, spring, and cap.

Install the shift tower, and a new oil seal inside of it. I greased up the new seal.

Install the front bearing retainer plate.

Lastly, install the reverse light switch.

This means you're DONE!!! :thumbsup:

Max :cheers2:

Squamer 07-14-2010 02:39 AM

Thank you so much for creating this!!! I wanted to rebuild my trans for the longest time....and being the visual person that I am, this is perfect!!

cvorden 08-02-2010 06:27 PM

Holy crap!!!! what an awesome write up!!

The time now is 04:55 PM.

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