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story and photos by Pete Jackson
This is only a partial rebuild as, at the time, only the brakes and axle shaft (wheel) bearings needed servicing/replacement. I found out later that I do have to pull the carrier and service the pinion bearings, and most likely the carrier bearings as well.
This article covers removal and replacement of the axle shaft bearings; due to the length and depth of the article, we have to split the two service articles.
Disclaimer: You are performing the work I describe in this article at your own risk. Follow all safety precautions and work within your experience level. If you lack confidence to do this fairly major surgery, farm it out to a trusted repair facility.
This Spicer 8.25” axle is common among Mopar rear wheel drive and 4x4 vehicles, most commonly used on the Jeep Cherokee (XJ) from the 1991 through the 2001 model years. Some early Mopar rear wheel drive cars also used it; as did some Dodge Dakota pickups and Dodge Durango SUVs also used the 8.25” axle, albeit with a greater width.
You may find this axle in earlier Jeep Cherokees, but the earlier the production year, the more rare. The ultimate unicorn of all the XJ rear axles was the Dana 44, which was included on my 1987 two-door XJ. The Chrysler/Spicer 8.25” is similar in strength, but uses “C” clips for axle shaft retention instead of bearing/shaft retainers like the Dana 44.
The 8.25” is often confused with the much weaker Dana 35 (“turdy-five”) axle, but the difference is easy to spot: the Spicer has a flat bottom and top to the housing and the pan, while the Dana 35 is round like a pumpkin.
Common symptions are:
In my case, I had all of the above.
Chock both the front and rear of each front tire so the vehicle can’t roll. Loosen the lug nuts with the 1/2” driver breaker bar, extension, and 19MM sockets. Release the parking brake (or you will not be able to remove the brake drums).
Raise and safely support the vehicle. You can use the jack on the center of the pumpkin to lift the entire rear end at once. Then place the jack stands just inboard of the lower shock mounts, on the axle tube. Lower the vehicle on to the stands, ensuring the tires are off the ground by about an inch. Remove the jack from the vehicle, it’ll be in the way otherwise.
Wheels, drums and cover were removed for this photo, but the placement of the stands is what’s important here.
Remove the lug nuts, then the wheels/tires. Set them aside in a safe place.
Remove the brake drums. If they won’t come off, they have either rusted to the axle shaft (common) or the self adjusters have compressed the shoes against the drums, preventing removal. If the latter is the case, remove the rubber plugs at the bottom of each backing plate and using two flat blade screwdrivers, release the adjuster lever and spin the adjuster star wheel to release the shoes from the drums. It’s tricky, but easy once you do it once or twice.
Once the drums are off, look for any leakage where the axle shafts enter the housing. In my case, both of my seals were leaking, and the bearings had failed. If need be, you may do only one side in a pinch. Chances are of one side is toast, the other is as well. You have both sides apart, so why not do both while you’re there?
Also, look at the top of the backing plates, where the wheel cylinders are located. If there is brake fluid present around the outside of the boots (like mine) than you will be doing a brake service as well. It’s much, mush easier to service the brakes with the axle shafts out of the way....
Check for any worn brake components. Shoes, springs, adjuster parts and the parking brake linkages. If any are worn, now is the time to take care of the issues.
Step one, removal of the differential oil pan (cover plate):
The bolts that hold the cover on could be any number of sizes, mine were 1/2” headed bolts. The thread diameter and pitch were 5/16-18.
Remove the rubber fill plug.
Place the drain pan under the center of the axle, below the differential pan. You will be removing all but the top bolt of the cover, but be sure the socket fits tightly on the bolt head, or you will round off the head, which makes removal much more difficult. You won’t be able to use an extension on the cover bolts as the fuel tank is too close to the cover in most applications. The 1/2” drive 6 point socket is the tool for this. Use either the 3/8” drive or the 1/2” drive ratchet for the stubborn ones.
Leave the top bolt of the cover loose, but still installed.
Once all but the top bolt are removed, loosen the pan by carefully sliding a box knife between the axle housing and the pan. If you bend the pan, it’ll never seal correctly on re-installation.
Once the seal is cut most of the way around, use a screwdriver or pry bar to gently break the seal the rest of way. The drain pan is still under there right? When the cover “pops,” all the gear oil will drain into the pan at once. You may get splashed with gear lube.
Once the cover pops, remove the remaining upper bolt. Set the cover aside in a safe place. Once you have the pan off, proceed to the next step. Clean the remaining fluid out using the brake parts cleaner.
You may have to rotate the differential carrier to access the lock pin. You can spin one tire or place the transmission/transfer case in Neutral and spin the driveline by hand to accomplish this.
I have no picture of the lock pin removal, sorry. It’s downright tiny compared the rest of the fasteners, using a 5/16” or metric equivalent for the head size in most cases. Use the correct size socket and ratchet to remove it. The threads of the pin have thread locker in them, so removal will be difficult, as it should be. This is a critical part in the assembly.
Clean the threads of the carrier with brake cleaner.
Here is the lock bolt, outside of the assembly. This one is damaged and had to be replaced. It’s ever so slightly bent. Also, note the scoring.
Once you have the pin removed, the differential cross bolt can be slid out. It’s ridiculously well lubricated, so it will likely slid out on its own. Place it in a clean, safe place.
Now, you’ll have to remove the “C” Clips from the shafts and remove them.
Once the shafts are removed, avoid rotating the differential. If it is rotated, you will dislodge the side gears; once dislodged, they are very difficult to get back into place. Ask me how I know?! You could also slide the lock pin back into place to hold the gears, since they ride on the pin. You would of course, have to remove the pin again to re-install the shafts.
Push the shaft into the differential carrier from the outside. You’ll hear the clip fall into the bottom of the housing. Then slide the axle shaft out of the housing. Place the on the hub (lug stud) end, upright. Otherwise, you risk the shaft getting bent and/or rolling away.
Repeat the push, then pull sequence for the other side. You should now have both clips in a safe place away from dirt. If they get dirty, clean them with the brake cleaner and a lint free rag.
With both shafts safely put aside, we can remove the bearing with the slide hammer and bearing remover set. Each remover works differently, it’s up to you to figure out how yours works. I didn’t get a picture of this step.
A few whacks with the slide hammer and my bearings and seals were out. You can remove the seals separately if only the seals need to be serviced, without removing the bearing. You will need only the seal remover for this. The bearing stays in the axle in this case.
Here are my bearings cleaned and prepped for inspection.
If they are blue, like these, and/or rough when spun like mine were, they are due for replacement. Mine are now paperweights.
You will have to inspect the axle shafts where the seals and bearings ride. If the surface is no longer smooth, the shaft must be replaced. In my case the shafts were perfect. No scoring, no excess wear. You can also measure the shafts to determine if the shaft is worn and requires replacement. I did find some specifications online, but by no means could I trust them for sure. It’s best to call a machine shop and see of they might have the correct info. Chances are, if the shaft isn’t scored or damaged, then you should be OK to re-use the shafts. If the shaft is bent or twisted, it must be replaced.
Now, we can re-install the bearings after inspecting the housing for any damage or wear. If the bearings were “tight” coming out, then you should be good to go. If the bearings fell out or came out with the axle, you’ll need to replace the entire rear axle assembly or find a shop that can repair it. There are no known repair bearings that will fit in the housing. You can find repair bearings that will fit an undersized shaft, but none where the race is larger to fit in the housing more tightly.
With the housing cleaned and inspected, place the new bearing against the housing opening and using the drift and hammer. Slowly walk the bearing into place until it’s fully seated, using the drift on outer race only. Be careful not to hit the rollers or the inner race as this will damage the bearing.
Once the bearing is in, lube it with some disc brake bearing grease. Pack it in there. It’ll thank you for it later! Dry starts are very bad for bearings. Once the gear lube works it way to the bearings, it’ll wash away the grease, this is OK. That’s what is supposed to happen. The bearings are lubricated by the gear lube as it work its way down the axle tube.
Now install the seal using the same technique, only use a piece of wood across the face of the seal against its metal shell. When the seal is seated evenly and against the bearing, you’re good to go. Using the drift on the thin shell of the seal can damage it, causing leaks. Lube the face (rubber part) of the seal with bearing grease. It doesn’t take much, just a thin layer is enough. Be sure to get the grease on both of the seal lips and in the valley.
Now, the tricky part, getting the shafts back in.
If you slid the cross pin back in, remove it.
Ensure the shafts are clean and free of dirt. Slide the shaft in from the outside and engage the spline in the side gear. You can very slightly twist the shaft to make the splines align. Just remove, if you rotate the carrier, the other sets of side gears will fall out.
Use a magnet and slide a “C” clip on the shaft, then push the shaft outward until the clip fully seats in the the carrier. Repeat for the other shaft.
Now, slide the cross pin back in, aligning the threaded hole on the cross pin with the hole for the lock bolt in the carrier. Install the lock bolt, tightening it snugly. It’s a small diameter bolt, so very little torque is required. Just snug once the head seats against the carrier will do the trick.
A new lock bolt will likely have thread locker on the threads already (this will make it difficult to thread it in). If you reused the old pin (or the new one doesn’t have thread locker pre-applied), then you will need to apply thread locker to the clean threads on the lock bolt.
You should now have something like this when viewed from the brake drum side (shown with the new brake components installed). If you are replacing the brakes as well, leave the shafts out until the new brakes are installed. You’ll have much more working room.
Now we can clean the cover and housing, then apply silicone sealer to the cover only (please for the love of all things good and holy, do not use orange high temp silicone; blue, black or gray are fine for this). A 1/8” bead is all that is needed. Be sure to go completely around the bolt holes and the entire cover. The previous owner of mine must have owned stock in Orange Silicone sealant; it’s a pain to remove and can set up as hard as rock. Clean-up was a painful experience.
You can paint the cover if you wish. Please pardon the mess on my work bench. I had a couple of different projects happening at the same time along with the service.
Now, slide back under the vehicle and place the cover back on, and insert one of the bolts (top preferred) to hold the cover in place while you secure the rest of the fasteners. Torque the fasteners to 15 ft/lb.
Let it cure for a few hours before filling the housing with gear oil. During this time, you can re-install the brake drums, adjust the brakes, and then re-install the wheels and tires. Snug the lug nuts. We will torque them later.
Now, with the sealant cured, fill the differential until oil runs from the fill hole. The amount varies depending by the vehicle, but about three quarts will do the deed. Once filled, replace the rubber fill plug. Mine was crispy and was leaking, so I replaced it.
Lower the vehicle to the ground and torque the lug nuts to factory specifications.
Take the vehicle for a test drive. Go slowly! Test the brakes for proper operation. Listen for any odd noises. Feel for any vibration. If there are none of each, pat yourself on the back and bask in a job well done.
My finished product before filling and replacing the rubber plug.
I left the bolts in their natural zinc finish.
Teaser pic from the brake service:
My original fears are true, and I will be doing a full rebuild this summer. The pinion bearings are definitely worn. While the heavy vibrations have gone away, I still have some noise and light vibration. I guess we can expect an update!
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