Previous, Part 1

Part 2: Rebuilding

The damage caused by the imbalanced front drive shaft was not as bad as I thought. Originally, I thought the splines on the output shaft of the 4x4 locker Axle Journal Neck (or Witches' Hat) were really buggered up. It turns out that the outer tops of the splines are machined down to improve the assembly of the front drive shaft to the locker which occurs in a inaccessable area while bolting the transfer case to the tube frame. I'll be showing an animated illustration of this concept in the final drivetrain reassembly entry of this blog.

Here is a step-by step illustration of the disassembly/reassembly process:

Remove the bearing cover
Use an impact driver with a phillips head to break loose the 4 screws holding the bearing cover at the narrow end of the housing.

Remove the circlip on the selector fork spindle (the long rod that the "selector fork" assembly pivots on) and pull the spindle out.  Be careful while doing this as there are several parts that might fall out and get lost.

Here are the items that will fall out when the rod is removed. Note the two rectangular blocks at the end of the selector fork.  They are only held in place by pins and the sliding gear mechanism! Keep track of them as they will easily fall out and disappear on the floor!

Now, we disassemble the assembly that is used to move the selector fork via the hydraulic acutator.

Find the plate on the side of the housing that has two phillips head screws holding it in place. There is a loaded spring behind this plate that will cause the plate to pop up and parts to scatter everywhere, so proceed slowly.  Carefully remove these screws and remove all the parts to the acutator assembly.

Now that the guts are removed, we can remove the driving shaft.

Here is a point where there is two ways to proceed.  You can knock loose the driving shaft, then remove the circlip or you can remove the circlip then knock out the driving shaft. Do whichever method you want to do.

Remove the big circlip that sits behind the bearing holding it in place.

Rotate the bearing cover until one of the tabs that the cover bolts go into on the housing is seen.  Rest the housing on this tab as indicated in the drawing and gently drive the driving shaft out with a copper hammer, deadblow hammer or a regular hammer and a block of wood.

At this point, I took the driving shaft with the old bearing, the oil seal and the coupling piece attached to a local machine shop (O'Reilley's Auto Parts on 23rd Street in Independence, MO).  They pressed off the coupling piece, bearing and seal then installed the new bearing and seal on the replacement driving shaft (which also had a fresh bushing installed in it).

Reassembling is done in the traditional reverse order. Here is a picture the rebuilt driving shaft inside the Axle Journal Neck before slipping the big circlip onto the shaft and pressing the bearing into its seat.

The circlip slips into a notch where the bearing is seated and acts to keep the bearing in place.

This is a picture from this website showing the best method for lubricating the oil seal on the Axle Journal Neck (see Jim LaGuardia's photo sequence of his differential rebuild project ). More on how I lubricated the seal in a bit...

I snapped the circlip into place and then pressed the bearing into place by gently tapping it into place with a heavy object and a block as indicated in the picture below (I used the old driving shaft, but a deadblow hammer would work just as well).

Here is a picture of the driver shaft in place.  Note the circlip that the new bearing rests on.

Here the selector fork and the shifter mechanism have been reinstalled.

This is the sealant Dennis Linden sent me to seal the Axle Journal Neck. It is called Victor Reintz Perfect Seal from the Dana Corporation.  I applied a thin coating on all bonding surfaces during assembly.

Here is the assembly of the bearing cover on the locker engagement mechanism.  Note the thin coating of sealant.  Someone in the past had rebuilt this unit with way too much sealant applied to joints.

Here is the bearing cover after the sealant was applied and cover attached...

...and the bearing cap in place after the sealant is applied.

Since I forgot to lubricate the bearing seal, here is what I did to fix the problem:

I poured roughly a quarter cup of 90-weight gear oil into the lubricating passage until the bearing was covered with oil.  Then I exercised the bearing to make sure oil had circulated thoroughly.

This method also tested the lubrication passage for blockage.

Finally, I made sure that everything worked correctly and that all extra sealant was removed from the area of the big O-ring and the mating surfaces between the Axle Journal Neck (or the "Witches' Hat") and the transfer case.

It's no fun trying to rip into some assembly while it is lying on the floor. Eventually, your back hurts, your legs hurt and, if you are working in dusty conditions, dirt can get inside whatever you are working on!  So why suffer?

This differential stand proved to be pretty handy during teardown. Using it, we were able to reach and work on nearly every part of the differential with ease. Here is a drawing with measurements and a lumber list.:

The picture has been resized to fit into the format of this blog.  If you are using Windows (tm), you can right click on the drawing and "save picture as..." to your PC and view it full sized. I am sure that you Macintosh and Linux guys have that technology in your browser.

We had two problems with this bench. First, the lack of access to the differentials’s drain plug. One should make a larger slot in the middle of the platform or, even better, drain the differential before removing it from the truck!

Second, the inability to get at the lower hex bolts holding the axle seals on the sides. We worked around this by lifting the differential up on 2"x 2" wood blocks for the hex bolts.

Here is the assembled table:

While the extensions on the sides of the table proved somewhat handy, a set of tall jack stands did a better job of supporting the axles during disassembly. The arms could have been six to twelve inches longer on each side to support the axles without jack stands...

Here's how things looked after we abandoned the blocks of wood method and used the jack stands under the brake housing method:

Notice how everything is nice and level, how the differential is actually resting on the table instead of precariously floating one inch above it. This was caused by the weight of the brake/portal housing and the brake drum levering against the aluminum differential housing. Shifting the support point from the middle of the axle to its ends solved the problem.

Disassembling the differential is fairly simple.

Loosen and remove the clamps on each axle's boot, then remove the four hex bolts that hold the axle seal on each side in place.  The seal is the aluminum ring pictured below that the boot is clamped to. It has a flange that seats against the upper and lower halves of the differential case. You don't have to remove the seal at this time.  It will fall out when the upper and lower parts of the differential case is separated. Note the "O" ring and the groove on the differential case where the seal fits. If it is torn or broken, you should replace them.



Remove the round plate on the front of the differential held in place by six hex bolts.  Yes, I know, the picture's contrast is terrible, but you can see several of the bolts around the edge of the plate in this picture. Two of them are shown in the picture below on opposite sides of the input shaft.



Next, there is circlip on the input shaft where you just removed the round plate.  Use a circlip tool (available at your local auto parts store) to remove this circlip.  

Handy Information:
Note that the pinion shaft pictured above has a hole machined into the end of it.  The output end also has a hole machined into it. Once the pinion shaft is removed, how do you tell which end is which?  The input end's hole is bigger and there is groove behind the splines where the circlip you just removed goes.

Next, there are two countersunk hex bolts on the front and rear faces of the differential. You can see them in the picture below at roughly the one o'clock and seven o'clock position.

These bolts hold the input and output bearings in place on the differential case.  The top one attaches to the top half of the case and the bottom one to the bottom half. Try as you might, the case cannot be opened unless you remove the top hex bolt on both ends. Trust me, I know...  Remove the top bolt first.  Do not remove the bottom one as it will complicate the disassembly.
Next, there are 8 large hex bolts that hold the two halves of the differential case together.  Remove them with the hex (or Allen) wrench in your Pinz toolkit.

As you remove them, those bolts that do not also hold down a brake line bracket sport a washer.  So when you re-assemble the case, don't freak out because there are more bolts than washers.  Just remember to put washers on the bolts without brackets.

Double-check to see if you remembered to remove the hex bolts in the axle seals as previously described. If you do not remove them the case will not come apart!

Being careful not to snag the brake lines, carefully tap the upper half of the case from below at the flange tab at the corners of the differential. The case should easily come apart. If it does not, you forgot to remove the top countersunk bolt on the input/output bearing plates or one of the bolts that hold the axle seals!

Here is a picture of the separated case:

Removing the pinion gear shaft and installing the Exec II parts

Start on either end of the differential, input or output, remove the bottom countersunk hex bolt.

Using a deadblow hammer or a copper hammer, gently tap the bearing assembly out of its seat in the differential.


(Photo courtesy Jim LaGuardia / http://www.sdp-pinzgauer.org/html/exec_ii_photo.html)

Once the pinion bearing assembly breaks loose, be careful when removing the bearing assembly from the shaft! There are two metal shim rings that are matched for this specific assembly!  Keep track of them as you take things apart and keep them in order with their associated bearing assembly. Here is a picture of one of the shims on the pinion shaft:

Photo courtesy Jim LaGuardia / http://www.sdp-pinzgauer.org/html/exec_ii_photo.html)

Now, repeat the same process on the other end of the differential.

Once you have removed the bearing assemblies, the pinion shaft is laying in the center of the differential.  Lower one or both of the axle ends a bit so that the side gears spread apart enough at the top to lift the shaft out. Be careful not to lower the axle-ends too much.

(Photo courtesy Jim LaGuardia / http://www.sdp-pinzgauer.org/html/exec_ii_photo.html)

At this point, I want to point out a bit of design that will be of interest to those who would like to increase the axle articulation. Take a look at the next picture:

Notice the groove in the tops of the pinion bearing assemblies?  Notice also the steel assemblies that slide on the outside of that bearing across the notch? Also notice that the side gears and axle shafts are fixed to the steel sidegear assemblies.  In the top and bottom half of the differential case, there is a pin that fits into that groove.  The pin keeps the two axle assemblies from moving too far causing possible damage. When suspension compression occurs, the springs and bump stops keep the sidegear assemblies from travelling too far and hitting that pin.  When the suspension droops as a wheel loses contact with the ground, the steel straps on the axles keeps the sidegear assemblies from travelling too far.  This is why using OEM travel straps are vital to preventing differential damage.

Once the Pinion shaft is removed, you can loosen the bolt that hold the side gears in place and remove the side gears.

Next is a picture from the LaGuardia collection showing the new bronze bearing inserts with perforations on either side of the pinion shaft. Also note the different bolt-and-nut assembly replacing the old bolt-and-threaded bushing system. The nut is partially hidden by the pinion shaft.

(Photo courtesy Jim LaGuardia / http://www.sdp-pinzgauer.org/html/exec_ii_photo.html)

Here are a few pictures that illustrate how the components are lubricated.

This picture of the old pinion shaft shows the famous "hole you can see through" at 90 degrees from the side gears.  When the differential is full, this unit is submerged at least to the centerline of the pinion shaft causing lubricant to flow into the hole.

Inside that hole lies the components pictured below; the gear bearing with widened center hole partially down the center axis of the bearing.

In this picture, the lubricant flows between the bolt and the bearing.

In this picture you see the space inside the bearing without the bolt.

Can you see the lump of goo on one side of the hole?

That goo is plugging up the lubricant passage to the face of the bearing where the side gear rotates.  When that hole is plugged, bad things happen!

Below is a picture of the damaged side gear bearing with the lubricating hole shown.

This is why you need to watch the differential lube levels like a hawk.  When the lubricant does not reach into these passages, bearing failure occurs!

Now you might say, "Hey Wait a second, Jim! How can I have a differential leak when the truck does not 'mark' its territory on the driveway?"

If the seal on the differential locker output bearing fails, any lubricant that ecapes gets trapped inside the steel casting that surrounds the "Witches Hat and supports the parking brake assembly. A LOT of lubricant must fill that space before you'll notice it on the ground.

If you dont have the tools to remove the old sidegears and bearings and install the new ones, you can take the parts to your favorite machine shop (often your local auto parts store has one in the back or can recommend several) and have the work done.

Reassemble in reverse order as above.

Here's a little table I put together to help apply the specified torque values during assembly for us metrically-enfeebled USAans...

Cut and paste it into your Pinzgauer repair notebook...

Continued, Part 3