10-Bolt Differential Upgrade

The 8.2 10-bolt rear first debuted in some '64 models alongside the older 8.4-inch third-member/dropout rear that had been around since the '50s. It owed some of its design to the 8.4, using the basic mounting dimensions of the 8.4's ring-and-pinion as the basis for the 8.2 design. The differential uses 3/8-inch mounting bolts for the ring gear, and has a 25-spline, 1.438-inch diameter pinion shaft. The stock axles were 28-spline, 1.20-inch diameter units. The early housings were cast from grey iron, while later housings were ductile iron.

The 8.2 was in production from '64 through the '70-71 model years (we've even seen the 8.2 pop up in a few '72s over the years as well). In 1970, the new, stronger 8.5-inch 10-bolt came out, and the 8.2 was put out to pasture once existing supplies were exhausted. For base model cars and moderate performance output, the 8.2 holds up fine. But when you start adding more horsepower, harder launches, burnouts, and all sorts of other performance abuse, the 8.2 can quickly eat itself. Usually it would be pitched in favor of the bigger 8.5 rear, or a 12-bolt if one was available.

Today the supply of used 12-bolts is dwindling fast, and even the 8.5s are starting to bring higher prices on the used market. Meanwhile, the old 8.2 languishes away, and supplies are plentiful. It was installed in Camaros, Novas, Chevelles, Caprices, Impalas, El Caminos, and Monte Carlos over its lifespan. Millions of them are still out there still, available for chicken feed when compared to the stronger units, and ready for rebuilding.

The aftermarket has parts available to boost the horsepower/torque capacity of the smaller 10-bolt, and with some upgrades these rears can withstand horsepower and abuse similar to the 8.5 10-bolt. To show off what you can do, we're gonna take the 8.2 from a '70 Malibu and make it a strong street and mild strip warrior.

Parts List

ETN-19603-010--Eaton differential, performance Posi, 28-spline 8.2 carrier
SAG-EV10-2C--Superior Axle & Gear 4340 chromoly direct fit 28-spline axles
CMB-14-0039--Summit Racing ring & pinion install kit (3.55 ratio)
SME-8510300--Summit Racing differential cover
BEN-33447--Wheel cylinders
SUM-B245--Brake shoe set
SUM-7104K--Summit Drum brake hardware kit
SUM-AD8208--Summit replacement aluminum brake drums

For the disassembly steps, we're going to use a spare 8.2 that the shop had sitting around, while the rear out of our subject Malibu was at the powder coater.
For the disassembly steps, we're going to use a spare 8.2 that the shop had sitting around
1 Note the rust on the ring gear. Even though this unit was still filled to the correct level with gear oil, because the gears hadn't turned in years and the top part of the ring gear was not immersed, the teeth rusted. If you're trying to get a car back on the road that's been sitting a while, pull the rear end cover and clean the teeth on the ring gear if necessary.
1 Note the rust on the ring gear. Even though this unit was still filled to the correct l
2 The first step is to remove the axles. To do that, the pinion shaft has to be removed, accomplished by removing the retaining bolt securing the shaft in the differential. Once removed, the shaft can be tapped out gently with a hammer and drift. Then the C-clips can be removed by pushing in on the axles, taking the load off the clips. A magnet tool will pull them right out, then the axles can be removed from the rear.
2 The first step is to remove the axles. To do that, the pinion shaft has to be removed,

3 With the axles out, the carrier barrier caps are removed. Be sure to mark which side and orientation the caps are removed from. Sometimes the factory will have marks cast into the caps, but it never hurts to mark them anyway. Like main bearing caps in an engine, the carrier bearing caps must be installed exactly how they were removed. Otherwise, you'll have a bear of a time setting the lash on the gears. After the caps are off, the carrier can be removed using a pry bar to coax it out of the bear races.
3 With the axles out, the carrier barrier caps are removed. Be sure to mark which side an
4 First step in removing the pinion is taking off the front yoke. You'll need an impact gun of some sort to remove the nut holding the yoke on, then a puller like the one shown to pull it off the pinion gear shaft.
4 First step in removing the pinion is taking off the front yoke. You'll need an impact g
5 Usually the pinion will need a few taps from a hammer to come out.

6 With the pinion removed, the next step is tapping out the old bearing race using a drift.
6 With the pinion removed, the next step is tapping out the old bearing race using a drif
7 Our new Eaton differential features a high strength steel case, forged web spider gears, and pyrolityic posi friction discs. The pyrolytic discs are similar to materials used on Indy Car brakes.
7 Our new Eaton differential features a high strength steel case, forged web spider gears
8a Our Summit Racing gear set and install kit came with a Richmond Gear 3.55 ring and pinion, along with all the bearings and shims necessary for the install.
8a Our Summit Racing gear set and install kit came with a Richmond Gear 3.55 ring and pin

8b The gear set is made from heat treated 8620 steel, and features a shorter pattern than the stock gear set, so under heavy load the pattern can spread the load more evenly across the teeth and not concentrate it on the outer edge, increasing the risk of failure.
8b The gear set is made from heat treated 8620 steel, and features a shorter pattern than
9a When you pull the old pinion gear out, there should be a shim like this on it. Be sure to measure the shim with a micrometer and note its thickness.
9a When you pull the old pinion gear out, there should be a shim like this on it. Be sure
9b When you install the new pinion gear, this measurement will give you a starting point for shimming the new gear.
9b When you install the new pinion gear, this measurement will give you a starting point

10 Moving to our now clean and powder coated housing, the first step is installing the new bearing races for the pinion bearings.
10 Moving to our now clean and powder coated housing, the first step is installing the ne
11 Here's an easy way to keep track of your pinion shims as you're figuring out what you need. This also works great for the shims on the carrier too.
11 Here's an easy way to keep track of your pinion shims as you're figuring out what you
12 To set pinion depth requires a special kit like this one. They can be easily had from the various tool trucks or specialty tool warehouses. Summit Racing lists a variety of pinion depth tools on their website, ranging from $20 to $189.95.
12 To set pinion depth requires a special kit like this one. They can be easily had from

13a After snugging down the bolts holding the ring gear to the new carrier, all the bolts are torqued down in a crisscross pattern.
13a After snugging down the bolts holding the ring gear to the new carrier, all the bolts
13b As you torque each bolt, mark the head with a Sharpie marker or something similar, so you know which bolts have been torqued, and which haven't.
13b As you torque each bolt, mark the head with a Sharpie marker or something similar, so
14 The install kit also comes with a new crush sleeve for the pinion gear. The crush sleeve helps to keep gear oil from leaking out the pinion shaft. Get this part wrong, and you end up with a puddle under your car.
14 The install kit also comes with a new crush sleeve for the pinion gear. The crush slee

15a To help with sealing, it's a good idea to smear some (we said some, not the whole tube!) silicone inside the pinion yoke before installation.
15a To help with sealing, it's a good idea to smear some (we said some, not the whole tub
15b Once done, the yoke can be installed and the pinion nut tightened down.
15b Once done, the yoke can be installed and the pinion nut tightened down.
16 Torquing the pinion nut down usually requires at least one extra set of hands, and a way to hold the pinion gear still while tightening the bolt. Even dry the pinion should turn fairly free. If you feel a lot of resistance or it requires a good amount of effort to turn, back the nut off, check your shims, then retighten.
16 Torquing the pinion nut down usually requires at least one extra set of hands, and a w

17 After installing new axle bearings in the tubes, we installed all of our new drum brake hardware from Summit.
17 After installing new axle bearings in the tubes, we installed all of our new drum brak
18 Just like with the pinion, we used the old carrier shims to give us a starting point for setting the gear mesh on the new ring and pinion.
18 Just like with the pinion, we used the old carrier shims to give us a starting point f
19a Including with installation instructions is a handy chart showing how the proper backlash should look on the ring gear.
19a Including with installation instructions is a handy chart showing how the proper back

19b After marking the teeth with some TK compound, we rotated it around, looked at the pattern, then adjusted the pinion and carrier shims until we got the pattern specified in the instructions.
19b After marking the teeth with some TK compound, we rotated it around, looked at the pa
20 Once set, the carrier bearing caps were torque down, and we spun the unit around to make sure it rotated properly.
20 Once set, the carrier bearing caps were torque down, and we spun the unit around to ma
21 Next, we slipped our new Superior Axle & Gear axles in place.

22 With the axles installed the C-clips are put back in place. Since our subject car is going to be mostly a street cruiser, the factory C-clip system will work just fine. If you're going to be hitting the strip with your Chevy, then a C-clip eliminator kit is the way to go. Just be aware you'll need to modify the ends of the axle tubes to install the system.
22 With the axles installed the C-clips are put back in place. Since our subject car is g
23 With the C-clips in place, the pinion locking pin is installed and secured with its bolt.
23 With the C-clips in place, the pinion locking pin is installed and secured with its bo
24 Here's how all the new internals look.The Eaton Posi with its pyrolytic clutch discs will provide smooth and quiet operation while giving us big smoky burnouts and two black lines instead of one. Eaton recommends mineral based gear oil only, along with standard Posi-traction additive.
24 Here's how all the new internals look.The Eaton Posi with its pyrolytic clutch discs w

25a The last step is installing our Summit Racing differential cover with adjustable load bolts for carrier bearing cap reinforcement.
25a The last step is installing our Summit Racing differential cover with adjustable load
25b The load bolts keep the caps from wandering and breaking under heavy loads. The bolts are lightly snugged down against the caps, then torqued to 10-foot pounds of load. Too much load will cause the caps to distort and break, so don't over tighten them.
25b The load bolts keep the caps from wandering and breaking under heavy loads. The bolts
26 Here's the rear back in the Malibu, looking like new. We also installed new control arm bushings, and a lower control arm reinforcement kit while everything was apart. This is a great time to replace said bushings if they're old and cracked, and the control arm reinforcement kit improves handling by reducing the flex and twist the stock non big-block arms have.
26 Here's the rear back in the Malibu, looking like new. We also installed new control ar

SOURCES
Summit Racing PO Box 909 Akron OH 44398 800-320-3030 www.summitracing.com	Classic Automotive Restoration Specialists Inc. 8235 Nautical Point Drive Belews Creek NC 27009 336-595-3900 www.classicautomotiverestoration .com
Superior Axle & Gear 9580 Commerce Center Drive Rancho Cucamonga CA 91730 888-845-0470 www.superioraxlegear.com	Richmond Gear Liberty SC 864-843-1276 www.richmondgear.com
Eaton 1111 Superior Avenue Cleveland OH 44114 800-328-3850 www.detroitlocker.com