Swapping Out GM Axles, Bearings, and Seals
If you’re building up a strip burner, that baby is going to need new axles. If you use the axles made for the tame 200-300 stock engine in your Camaro, Trans Am, or whatever with a powertrain that pumps closer to 1000 horses, you’re going to run into serious problems. Like, you won’t even last for the burnout; you’ll spin the splines right off the ends of the axles as soon as you hammer it. Swapping out the weak old axles for some new ones, say from Strange Engineering, isn’t hard. To be honest, it’s also not all that time-consuming. It’s just messy. Let’s walk through the process of installing new axles in a GM ten- or twelve-bolt rear-end, shall we?
What You’re Going to Need for This Project
I’m betting that other than the replacement parts and the gear oil, you probably already have everything you need to complete this project. Here’s the list:
• Jack and two jack stands
• Sockets and ratchet
• Lug wrench
• Catch pan
• Gasket scraper/cleaner
• RTV Black
• New differential housing cover gasket
• Gear oil 80/90W –Maybe a quart
• New axles
• New axle bearings
• New axles shaft seals
• Axle bearing puller
• Seal installer or block of wood
• Axle bearing installer
• Prybar or good-sized flat screwdriver
• Two blocks of wood
Step 1: Raise and Support the Car
Park the car on a flat and level surface, not in your driveway, keep it out of gear/Park for now. Block the front and rear of at least one front wheel. Using the lug wrench, loosen the lug nuts on both rear wheels. Place the jack under the differential and raise the rear end until the wheels are clear of the ground. Place the jack stands under either the rear frame rails, the lower shock mounts, or the axle housing on either side and slowly lower the car onto them. Remove the lug nuts and wheels.
Step 2: Remove the Differential Cover
Lower the jack all the way and pull it out from under the car. Slide the catch pan under the differential housing. Using the ratchet and a socket, usually half-inch or 9/16-inch, remove the bolts on the cover. There’s going to be either ten or twelve of them. You want to leave three or four in but removed most of the way to catch the cover.
Carefully pry the cover off the differential housing. Don’t try and pop it off all in one shot, you’ll bend it. Tap a screwdriver or small prybar between the cover, remove it, move 45 degrees, and repeat. I like to start at the bottom, move 45 degrees clockwise, and then 45 degrees counter clockwise from the very bottom.
Step 3: Remove the Brake Parts-Disc Brakes
First, you need to pull the caliper. The two bolts securing the caliper to the caliper bracket are usually either 9/16-inch or 14 mm. To make removing the caliper a little easier, you can use your prybar or screwdriver to carefully pry the outer tabs/wings away from the rotor.
Remove the bolts and pull the caliper off the rotor. Use a wire or string to hang the caliper from the leafspring or brake hard line. Don’t let it hang from the hose. Next, remove the two bolts securing the caliper bracket to the axle housing. These are normally ¾-inch or 19 mm bolts.
With the bolts out, remove the caliper bracket, set it aside, and then remove the rotor. If the rotor doesn’t want to come off easily, there are two holes in it, across from each other, that you can thread bolts into which will push the rotor off. You should now be looking at the axle and brake backing plate.
Step 3: Remove the Brakes-Drum Brakes
This is ridiculously easy. Simply pull the brake drum off the axle studs. If it sticks, you can smack the flat part of it a few times with your hammer.
Step 4: Remove the Axles
On GM 8.2-inch and 8.5-inch pumpkin gear ten- and twelve-bolt rear ends, there’s a small 5/16-inch bolt that locks axle pin in place. The axle pin is a chrome pin that keeps the axles from floating inward and allowing the C-clips to fall out. Rotate the driveshaft until you can see this bolt.
Now, put the transmission either in gear (with a manual) or in Park (with an automatic) to keep the driveshaft and rear gears from turning. Remove the axle pin bolt and set it aside. Push the axle inward, reach into the gear housing, and remove the C-clips.
Now, carefully remove the axles. Slowly and very carefully slide the axles out of the axle housing. You’re protecting an inner bearing and seal inside the differential when doing this, not the outer bearing and seal we’re replacing.
Step 5: Remove the Seal and Bearing
If you want, you can use a specialized seal removal tool, but with the axle in hand, you’ve got all you need already. Simply place the end of the axle behind the inner lip of the seal and push down on the hub end lightly. The seal is now sliding down the axle shaft towards the hub.
Pulling the axle bearing is a little more involved, though. For this, you need a specialized bearing puller. There are a couple different types of this tool. Mine is a hardened steel flap attached to a slide hammer. You can loan or rent one at your local part store, like Autozone.
The tool is installed and held firmly behind the bearing. The slide portion of the slide hammer is then slapped, hard, against the outer stop. This is repeated until the bearing comes out. Another style of tool has the puller installed behind the bearing and a cap set against the outside of the axle housing. A bolt is then tightened down with a wrench until the bearing comes out. Repeat Steps 3-5 on both sides.
Step 6: Installing the New Bearing and Seal
In the old days, this was a two-step process, first, the bearing was installed and then the seal was installed. Timken now has an integrated bearing and seal unit that I highly recommend. It turns a two-step process into a single step.
Either way, you need a bearing installer tool. Find the cup that just fits inside the axle housing, place the bearing on the tool, and smack the tool’s handle with a hammer until the bearing is fully seated. Next, repeat the process with the seal. If you use the new Timken integrated bearing and seal, smack the tool until the sound you hear when striking the tool with the hammer changes. This indicates the bearing is seated. Repeat this on the other side.
Step 7: Install Your New Axles
Once you’ve got the lug studs installed (unless the axles came with the studs pre-installed) on your new performance axles, it’s time to install the axles. Carefully slide the new axle into the axle housing, using the hub to keep the end of the axle shaft centered as much as you can. Slowly slide the axle into the housing as far as it will go.
Once the inner end of the axle shaft bottoms out against the carrier assembly inside the differential, carefully move it around until you find the opening and can fully seat the axle. Repeat this on the other side.
Now reach inside the axle carrier inside the differential and ensure that the axles are fully seated. If not, wiggle and slightly rotate the hubs while pushing towards the center of the car until they are fully seated. Again, reach into the axle carrier, this time, while holding the C-clip./ Make sure the worn side of the C-clip (if using the old ones) is toward the center of the differential and slide it over the end of the axle. Push the axle out. Repeat this on the other side.
Finally, slide the chrome axle retainer pin that you removed in Step 4 above back into the carrier between the axles, making sure that the screw hole is pointed towards the passenger side. Reinstall the 5/16-inch bolt and torque it to eight to ten pound-feet. It’s a good idea to put a few drops of red Threadlocker on the threads before reinstalling this bolt.
Step 8: Replace the Differential Cover and Refill with Gear Oil
Use an old rag and wipe the old gear oil into the catch pan. Next, completely remove the old cover gasket from both the differential housing and the cover. Wipe both surfaces clean with a rag. Make sure that every bit of old gasket is removed. Remove the magnet from the cover and thoroughly clean it. You need to get every bit of metal shavings off the magnet before sticking it back onto the cover.
Next, check the bolt holes on the cover. If they aren’t flat, place the cover upside down on a socket and tap the bolt holes with a hammer to flatten them. If you don’t do this, the cover can leak.
Apply a light coating of RTV black to both the housing and cover and push the new gasket into the housing. Hold the cover up against the housing and get all ten or twelve bolts started and hand tight. Torque these bolts to twelve pound-feet. If you tighten these bolts too much, you’ll pull the bolt holes in and cause the cover to leak.
Slide under the car from the rear passenger side with a ratchet and short extension. Locate the square drive differential housing plug. Use the ratchet and extension to remove the plug. Using 80/90 weight gear oil, refill the differential until gear oil just begins to seep out of the plug opening. I like to use a one-foot length of small hose over the nipple on the gear oil bottle to have better control over the flow of the gear oil. Reinstall the diff plug.
Step 9: Brakes, Tires, and Lower
Wipe down the backing plates at the outer ends of the axle housing. Reassemble the brakes on your car. Slap the tires on and run the lug nuts down as much as you can with the rear in the air. Slide the jack under the differential housing and raise the car off the jack stands. Remove the jack stands and lower the car until the suspension begins to take the weight of the car. Finish torquing the wheels and lower the car the rest of the way.
You’re going to want to test drive the car for a few miles, making sure to take some left and right turns. This makes sure the gear oil is evenly distributed in the differential and down the axle housing tubes. After the test drive, raise the rear evenly and recheck the level in the diff. Pull the plug again and stick your pinky into the plug opening. You want the gear oil to be about a ¼ inch below the opening. Top it off as needed.