Rear Axle/Differential Rebuild AAR

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Jun 8, 2018
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Southern Indiana
ETA, sorry for the length but I really wouldn't be putting this info here if I didn't feel it was important. Differential repair is a complicated process that some liken to "an art" This information is the result of many, many, many hours reading online forums etc plus a generous dose of learning the hard-way. The new diff. has been in for about 400 miles now and I'll check back occasionally to report any problems or problem-free mileage...

Unfortunately, my differential carrier bearings went out recently. With no reputable local shops to do a repair, I decided I trust myself more than the local shade-tree mechanics. I've never done a rear diff/axle before so it was all new to me. I learned some lessons along the way that I would like to pass on.

General info: The 1/2-ton trucks/SUV's have what is called a C-clip axle. There is a small C-clip on the axle, inside the differential that holds it in place. The wheel-bearings (and seals) run directly on the axle, there is no inner race for the wheel-bearings. The differential carrier bearing pre-load is not adjustable with a nut like many larger differentials, it's shimmed, with a kit that the dealer has, and you don't have.

I knew with 120k without an axle replacement there was a chance my axles would be worn where the wheel-bearings ride. There are 2 solutions to this problem, #1 "repair bearings, and #2 replace the axles, bearings, and seals.

The repair bearings incorporate a narrower row of roller AND the seal all in the same housing. Option #2 is self-explanatory. It’s a bit more costly but sets you back to the original state.

My axle had some wear, I think primarily due to all the metal fragments from the disintegrating carrier bearings. This gave me 2 problems. #1 I had a hard time getting the C-clips out of the axles. I simply couldn’t get the axles in far enough to get the clips to fall out. I could push them in but they would flex out. I eventually figured out that the grooves worn in the axle by the seal were “HOLDING” the seal so as soon as I pushed the axle in, the seal pulled it back out. I used ratchet straps to pull and hold the axles in so I could remove the clips. The 2nd dilemma was replace it all due to worn axles or go for the repair bearings to extend the life a bit more. I opted for the repair bearings, at a cost of ~$90 instead of $250 for new axles, bearings, and seals. IMHO, this was my first mistake. With hind-sight being 20/20, I’ve since realized that trying to save a buck usually costs in the long-run. The repair bearings (even quality one from Timken) are full of problems. I didn’t know that at the time. #1, to get the seal to run in a new spot on the axle, the bearing sticks out the end of the axle tube ~1/4”. This made reinstalling the C-clips very hard. I ended up damaging the seals just from putting enough inward pressure on the axle to get the C-clips in. I didn’t know this until it was ALL back together and leaking oil out the axles. Removing the C-clips to replace the bearings/seals a 2nd time was even harder. I ended up taking a BFH and smashing the axles in (intentionally crushing the seals) so I could get enough clearance to get the C-clips off. That was the first $90 (plus oil, gasket, etc) down the drain. Skip the repair bearings and get the original style plus new axles & seals. It’s not worth a 2nd time tearing into it.

Carrier removal: This is simple, after axles are out, remove 4 cap bolts. MAKE SURE to make a mental note of which cap is on which side, a picture is best to know exactly how it all goes back together. The caps cannot be switched from side-to-side. If the carrier is too tight and hard to remove, put a small ratchet strap around it and hook the other end to the bumper/hitch to help pull it out. Mine fell out because the carrier bearings were so far gone there was no load on it. Shims: you may be able to re-use the shims, if so keep track of where they go. IMHO, more on this later but it’s best to not re-use these shims and I’ll explain why (later, I said).

Pinion bearing replacement: I used a Timken differential rebuild kit that came with new pinion & carrier bearings, new seal, nut, and crush-sleeve. Minus the fact that Rockauto sent me used* parts in that kit, it’s well worth it. *[carrier bearings were used and the pinion nut was used & stripped out] There are some other parts you’re going to want as well (more on that later). The pinion bearing replacement is straight-forward if you’re not changing your actual gears. Remove nut, remove yoke, replace nut partially and with a rubber mallet pound on the pinion (you MUST remove carrier first). The front pinion bearing is what is holding the pinion in. You’re driving a bearing race off the pinion shaft so it’s going to take some work. The last whack will more than likely send the pinion out the back of the case onto the floor. I recommend a large box with lots of bubble wrap to catch it. Do NOT be tempted to use any hammer other than a rubber or leather mallet on the pinion. You will likely damage the pinion threads. Like a dummy, I stepped it up to a brass hammer and managed to mess up the threads. Thankfully, I have a machine-shop in my garage so I was able to repair them on-site. Removing the bottom (large) pinion bearing from the pinion shaft is tough. You may have to use heat but before that I would go to Autozone and rent (free) their large bearing splitter and the puller that is meant to go with it. These are separate items so you have to get both. Even though the bearing splitter looks like a wedge that is meant to be clamped together to squeeze the bearing off it’s not. You will ruin the pinion depth shim that is between the bearing and the pinion gear. This shim could be reused at long as you’re not changing the actual ring/pinion themselves. I reused mine. If you ARE changing gears you will need to re-shim. There are some tricks of the trade to figuring out the right shim without putting the new bearing on, checking the fit, pulling the bearing and trying again. I won’t get into too much of that but it involves using a carbide burr on a die-grinder to open up the inside of the OLD bearing so it will slide on easily. Once you’re ready to put it all together you need the new crush-sleeve. This is a once & done thing. If you aren’t ready for final assembly then don’t get the new crush-sleeve out yet. This sleeve literally “crushes” to get the proper bearing pre-load. My yoke came off with a “silicone” type stuff in the splines. Thinking about it, the splines are directly connected to the inside of the case (the seal runs on the OD of the yoke) so oil could seep out the splines. I cleaned them out and put new silicone in the splines. The force necessary to crush the crush-sleeve can be up to 400 ft-lbs. You MUST have an impact to do this. I had to hammer quite a bit with mine to get it down. The amount of force & torque on that nut is really hard. I suggest you add a bit of oil to the pinion threads the ensure the nut doesn't gall. Some call for thread-locker; my nut was a self-locking type but if yours isn't then thread-locker should probably be used so skip the oil and hope the wet thread-locker is enough lube for the threads. Stop frequently and check how much the pinion moves in the housing. The carrier bearing preload will remain at 0 until all the “slop” is taken out of the bearings by the crushing of the sleeve, then from there the pre-load will increase VERY FAST. So you want to check frequently until the pinion doesn’t seem to slide in/out anymore. From the point that bearings first make contact to the point that the pre-load is at max only takes about 1/8 of a turn of the nut. So once the bearings start to make contact (don’t slide anymore) to the point that you’ve gone too far will happening quickly. It’s best to use a paint-pen etc to put some witness marks on the socket so you can visually see how far it has turned and stop and check pre-load frequently. The preload spec for new R&P bearings is 14-19 IN-LB. This isn’t much. As a matter of fact, not even my small gunsmithing torque-wrench would go down this far. There are ways to make a make-shift “torque wrench”. Torque is just a measure of how many lbs of force at what distance from the center pivot it takes to turn something. IE, 14 IN-LBS could be 14 lbs of force 1 inch from the center, or 1 lb of force 14 inches from the center, or 2 lbs of force 7 inches from the center. Just multiply the force by the distance keeping your units consistent. The easy way to measure the torque is to attach a dowel rod ~40” long perfectly centered in the yoke. Make a mark at 14 & 19 inches from the center. You should be able to hang a 1 lb weight in between the markets and get it to turn. If it does not turn with the weight between those marks it’s too tight. You need to remove the yoke, get a new crush-sleeve, and start again. If it does turn with the weight between those marks then verify that it does NOT turn if the weight is slid inside of the 14” mark. If it still turns with the weight inside the 14” mark it’s not tight enough, go a bit more and try again.

Carrier: #1 STOP, inspect your carrier & the spider gears inside thoroughly, especially if you’re having any rear-end “clunk” that isn’t due to excessive backlash or a bad u-joint (I was having this clunk). It’s pointless to replace bearings on a carrier that needs rebuilt/replaced. Unfortunately, I thought the clunk in my rear-end was due to the bad carrier bearings. It turned out to be bad spider gears which wasn’t discovered until it all went back together the first time and was still clunking. Deep down I had suspected they were worn but I guess I didn’t want to admit it. If you’re replacing bearings, then clean the carrier out very well. I bought a few cases of brake-cleaner and nearly used them all. You DON’T want a few metal particles from the last failed bearing killing the new ones as well. If you're replacing the carrier (like I did the 2nd time), so-far so good with my Truetrac. I found it at Summit Racing for $469 and they had a $50 off $500 coupon, plus free shipping. I scoured the web and that was the cheapest place I could find it. Total cost, including tax was ~$440.

Removing the carrier bearings can be tough. There are recesses in the OE G80 carrier to attach a puller but that didn’t do any good. My bearings were on there TIGHT. I had to use heat AND the puller. To do this you need to cut the roller cage off and remove the rollers. When using heat you don’t have a lot of time until all that heat transfers to the carrier and starts to ruin heat-treat. Have the puller on the bearing and have some tension on it (about as tight as you can get the push-bolt with a normal wrench). Having a power tool nearby for quickly spinning the push-bolt down (impact, drill w/ socket, etc). While heating the race and only the race, watch for it to slide a bit. The tension on the puller should pull it up a bit as soon as it loosens. It also doesn’t hurt to check the push-bolt tightness occasionally as you’re heating. As soon as it loosens up hit the bolt with the power tool and it should literally slide ride off, like a hot-knife going through butter. It really is that easy. Precautionary statement: Have some cold water handy. This can be used to put out a fire, or cool things back off if it’s not working. The last thing you want is a ton of heat soaking into your carrier. Pressing new bearings on is fairly simple. For those that don’t know what you’re doing, DO NOT, EVER, use the new bearing race to press on a new bearing. What you want to do instead is to use the old inner race, butted up next to the new inner race, to press it on. The takes the load off the rollers themselves and puts it on the part of the bearing that isn’t susceptible to damage. After the new bearings are on set the carrier aside.

Housing: Clean this out good… like really good, but not until you've pulled out all the parts possible (I left the ABS reluctors in because it looks like I would have to damage the retainers to get them out). To pull the axle bearings it’s easiest to get the universal puller set from Autozone (once-again, free rental). The semi-round thing goes inside the bearing, flips out to engage the bearing, then the slide hammer pulls it. The tubes have many, many recesses and hidey-holes to hide metal shavings. You will use lots of brake cleaner and compressed air to get it out. After you’ve removed all bearings, seals, and race, you should also remove the ABS wheel speed sensors at the end of the axle tubes. These can be tricky to remove if they’re even slightly rusty. They are Torx bolts and have a tendency to strip the heads. I sprayed penetrating oil and let it sit for a good long time. Then I tried, I could see that the heads were still going to strip so I stopped. I pounded on the heat of the bolt for 2 reasons. #1 to break loose any possible rust, and #2 This smashed the head in a bit, tightening up on the Torx bit. I then tapped the Torx bit tightly into the bolt and carefully turned. I was certain it was going to strip the head, then right before the head gave way, the bolt popped loose with a snap… VICTORY. Same thing for the other side. Now, see that nice metal reluctor ring? All those grooves trap a ton of metal in against the axle tube. Spray, turn, spray, turn, spray turn… I think I used 2 cans of Brake cleaner per side just for this part. I also sprayed in the ends of the reluctor by lifting it up and spray all around the side. Now, use a rag, pushed by a long stick through the axle tubes to push everything to the INSIDE. Pushing to the outside will just bury more metal under the ABS reluctor. Unfortunately, right behind where the carrier bearings sit is a recess, this will grab most of the metal pushed through the axle tube. Clean this with lots and lots of q-tips… LOTS of them. Continue the process of brake-cleaner, q-tips, and rags pushed through the tubes until they’re coming out clean and white. This will take some time. Use brake cleaner to spray up into the pinion mounting locations and oil passages. Did I mention to get lots of brake cleaner? It’s best to just buy it by the case when it’s on-sale. Menards has it on-sale for $1.89 per can this week. They looked at me a little weird when I got 5 cases.

Once the housing is cleaned it’s time to put it back in. The pinion install directions are above. The carrier is next. Note: the OE shims are 1-piece cast-iron. They are very brittle, if you haven’t already broken them by dropping them then you’re lucky. The unlucky part is that if you didn’t read this all the way through, you probably tried to re-use them and found out that they’re very brittle, just like me. This will set you back a few days while you wait for shims to ship to you. Because if you’re like me, no local places have carrier shim kits. The likes of Autozone, Advance Auto, etc will happily sell you a pinion shim (which is the least likely of the shims that would need changing) but they don’t have carrier shims. Which is messed up. I swear they don’t have a clue what they’re doing when they decide what parts to carry. Anyways, do yourself a favor, before you even start this project get yourself a Yukon Gear Super Shim kit, or a Motiv Super Shim kit. They are both made in similar fashion, and both of their websites are equally elusive on providing the details. I cannot say what exactly comes in the Motiv kit because I ended up with Yukon’s kit (it was Prime eligible and I needed it asap). The good: The kit consists of a thick inner shell and a thick outer shell. You place the actual shims between these shells. The thing that makes these 2 super shim kits stand out is that the inner shell has a raised lip on the ID so that it holds all of the shims and the outer shell aligned. The shims cannot slide apart like a traditional shim stack-up would. This, IMHO, makes it worth it. The bad: In my case, for both times I installed the carrier I came upon a conundrum. The smallest of the shims included in the Yukon kit is .006” (not sure about the Motiv because they won’t tell you on their website). The kit also includes some .007, .010, .030, and a .050” shims IIRC. With this you can get any combination from .006” up only skipping a max of .003” from 1 thickness to the next. Unfortunately, if like me, you need .002” of shims between the inner & outer shell to get the right gear backlash at the right bearing preload you’re SOL. The backlash spec is .003-.006” (for 2-cut gears). The first time I put the carrier in I was at .0065” with only a single .006” shim in the right side. Removing this shim and placing it in the left side (to maintain preload) would have decreased my backlash .006” x 70% (backlash changes 70% of what you move the carrier) = .0042”, which would’ve put my backlash at .0065 - .0042 = .0023”. I called Yukon; they’re tough to get ahold of but finally got somebody on the phone that went in the back and asked. They told me on a used R&P where there wouldn’t be any break-in heat etc, .002” backlash would be fine. So I took that .006” out… When I put the carrier back in the next time (w/ the new Eaton TrueTrac) it ended up a bit on the low side so I put the .006” spacer back in and my backlash spec was right on .006”. I would’ve preferred getting it a bit tighter but my only option was on the loose end of the spec, or too tight… As far as actually installing the carrier, this gets tricky. You’re trying to keep shims in place while holding and installing a carrier that has 2 loose bearing races on the end. Having the car on a lift with a 2nd set of hands is huge. The other option is to just remove the entire rear axle. This makes cleaning easier also, but then you have to mess with brake lines/cables, all the suspension components etc. If you don’t have that luxury what I found the first time (done on blocks in my garage) is to put the carrier on your groin area while laying on a creeper, feet pointed to front of vehicle. Then roll in with 1 leg on each side of diff housing. When you get under there lock your knees on axle tubes and roll carrier up in. The shims should be installed in place, up against the axle tubes BEFORE the carrier. DO NOT try to drive the shims into the gap after the carrier is in place. The fit should be tight; according to my research it’s impossible to get the preload too tight without the axle-spreader tool. My research also indicated the axle-spreader isn’t necessary. It’s ok if the bearing races try to “spring out” at an angle, just lightly tap them back into alignment with a nylon hammer as you push/tap the carrier into place. Why nylon? Rubber & leather mallets have a tendency to hold dirt etc. You really don’t want to be smacking dirt into your new bearings. Nylon, wiped clean, will show any dirt left on the surface. Once you get it in most of the way you can use the bearing caps to pull it in the rest of the way, just be careful to pull evenly on the bolts so you don’t crack a cap or tweak the bearings/carrier. You will likely get good at this because you’ll have to do it once and check the backlash, adjust your shim stack, and go again. Removal gets to be tricky. I dropped shims & races on the floor numerous times... which requires a meticulous cleaning and re-lubing to prep for reinstall. As before, if it's tight (it should be) you may have to wrap a ratchet-strap around the carrier to pull it back out.

Other insights:

I’m not sure how much preload was on my previous carrier bearings but I was informed that my “whole rear-end was replaced at 81K miles at the dealership”. That shows up on the Carfax as a transmission replacement but that dealer said the rear was done when the tranny was done. Why did my carrier bearings last only 40k miles? I know this much, I pulled out .020” of shims that I simply could not fit back in there without a housing spreader. I suspect the dealer used a housing spreader and they DID manage to get the preload too high. My R&P looked brand new, but the carrier had very worn spider gears. I suspect there is a discrepancy between the “whole new rear-end” I was told was in the vehicle and in-fact, it was just new bearings and a new R&P on the old carrier.

Because I still had the clunk, and had to tear into it a 2nd time to fix the leaky axles, I decided to just ditch the factory G80 and go with an Eaton Truetrac. I should have done this the first time but I was under time constraints, working by myself, without a lift, and I was hoping to save money. After I realized I had to pull it back apart and I was already putting new axles etc in, I decided to say screw-it, I'm doing it right with no expense spared as far as a "mostly factory unit" goes. NOTE: the Eaton uses different bearings (but same races). The bearings are LM603049 and the races (same as OE) are LM603012 for the 8.6" 10-bolt GM axles. These part numbers are mostly universal across all makers. I also decided I wasn’t tearing into this again so I replace everything except the R&P. New carrier, all new bearings again, new axles, axle-bearings, and axle-seals. All in, it cost around $750 in parts but it was worth it if I don’t have to touch this thing again.

I chose Timken bearings for ALL bearings. What I got was ALL Timken boxes with various manufacturers bearings inside. The repair wheel bearings were Linkbelt brand. The OE style wheel bearings were KOYO, which is the OE maker for all the rear-end bearings. All the taper bearings were Timken bearings in the boxes. Interesting note: the Timken boxed KOYO axle bearings were cheaper than the ACDelco OE bearings... same exact bearing in the box...

Replace all cheap parts that are easier to do now: IE, the brake backing plate (or dust shields) are 1-piece and require axle removal to replace. While Dorman makes a 2-piece AM shield (for a cost) it can still be challenging to get the 1-piece off at a later date unless they’re completely rusted away. Just go ahead and pre-emptively replace these while the axles are off and before you clean the axle housing. The 1-piece are stupid cheap online. Don’t make the mistake I did and tell yourself “maybe I won’t need them” then decide at the last minute, when it’s too late to order them online, that you should replace them. You’ll pay inflated local costs and the only one they have is the Dorman… yuck. I did it anyways because they really did need replaced.

Pre-lubricate all bearings before installing them. Use the same gear oil you’ll be using to fill the diff. IE, don’t pre-lube with grease etc, pre-lube with the fluid that will be lubricating them from here forward.

Another thing, you know where I told you to clean everything really, really, really well? You still failed. It's impossible to get it all cleaned out. Trust me. I tried my best. I put the diff back together, realized the seal were leaking but couldn't fix them right away. I put about 800 miles on it before the 2nd tear-down and installing the true-trac. I found a couple larger metal shavings that I suspect were hiding behind the ABS reluctors or in the G80 carrier, plus lots of fine metal that you could see suspended in the oil. I highly recommend you put some cheap oil in it, run it 100 miles, change it. Put the good oil in it, run another 500 miles and change again. This will ensure that any metal flushed out in the process of running doesn't get to float around in there very long (causing damage) before you get it out of there.


I’m not going to list specs here, there are plenty of other places they’re listed. Be ware of 2-cut vs. 5-cut gears. OE gears are 2-cut I believe, which calls for less backlash. Some older and some aftermarket gears are 5-cut and require more backlash.

While pinion bearing preload is listed, there really isn’t a clearly defined spec for carrier preload. I just got it as tight as I could w/o the housing spreader tool.

Lastly, a list of tools and parts.

Tools (besides the obvious necessities and in no specific order):

-Impact capable of 400+ ft-lbs & 1-1/4” socket for pinion nut (not necessary if not removing pinion)

-Grease for holding shim stacks together

-Axle bearing pullers

-2-jaw puller for carrier bearings

-Hydraulic press for seating new bearings

-Various sockets or bearing drivers for installing new bearings.

-Dial indicator at minimum, or dial-test indicator (recommended) and mag-base for measuring backlash

-Emery cloth to clean seal surfaces

-Wire brush for removing rust and gunk

-Nylon hammer

-Soft mallet or dead-blow hammer

-Seal & bearing drivers (or assortment of large sockets and such)



-Differential Rebuild kit (indiv. parts: carrier bearings x2, carrier bearing races x2, pinion bearing large & small, pinion bearing races large & small, pinion nut, pinion crush-sleeve)

-Axle bearings and Axle seals (both can be replaced by repair bearings but I would not recommend that)

-Differential cover gasket

-New axles (recommended if your vehicle has higher miles or a rough life)

Fluids & cleaning aids:

-Lots of brake-cleaner


-Lots of clean, lint-free rags (I use t-shirts as a “mostly lint-free” rag)

-Oil (this depends on the diff you’re installing, the Truetrac calls for std oil, not synth., your choice may be different)

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