Chevy 10-Bolt Rearend Upgrades - Super Chevy Magazine

This 8.2 10-bolt has been modified from the '71 Monte Carlo to fit under a Chevy truck. That's why the brackets and coil spring pads are missing.

This 8.2 10-bolt has been modified from the '71 Monte Carlo to fit under a Chevy truck. Th

When it comes to gears and rears, many concentrate on the high-end, bulletproof differential and axles-and for good reason. When it comes to the transfer of horsepower and torque, a vehicle's rear gear and axles can be the weakest link in the chain.

What if the hot rod is not a racecar or mega-horse street flier, but rather a cruiser running in the mid-400-horse range that will never see the track? Building a rear end capable of withstanding 800 horsepower and 6,000-rpm clutch drops with slicks is certainly no disadvantage, but is it always cost-effective to do so? Throughout the '60s and '70s, GM vehicles came equipped with a myriad of gear ratios, axles, differentials, and so on. Identifying and even modifying these can be a bit flustering, especially if the rear-end came from another car or swap meet. There's no telling what might be inside. Recently Jim Allen and Randy Lyman wrote a book called Differentials, Identification, Restoration & Repair. Before that there was the Chevrolet Chassis Service Manual, and that was pretty much it.

Chevy 10 Bolt Rearend Differentials Book

Differentials, Identification & Restoration by Jim Allen & Randy Lyman is a 378-page book filled with photos, facts, tech tips, and step by step re-build how-to stories concerning many of the domestic differentials. All in all, it's a very good read, especially if you plan on doing the job at home.

Differentials, Identification & Restoration by Jim Allen & Randy Lyman is a 378-page book

The particular rear end in this story came out from under a 1971 Monte Carlo. According to Jim and Randy's book, the early '70s were kind of a mixed bag when it came to rearend gearing and sizes. The 1971 A-bodies were no different, some had the coveted 12-bolt while others had the 10-bolt and the 10-bolts also varied in size as well, using both 8.5-inch and 8.2-inch diffs. The 8.5 is by far the more desirable of the two because of the larger ring gear and larger 1.625-inch diameter pinion.

As circumstance would have it, the rear end we pulled from the Monte had an 8.2 ring gear inside. Allen and Lyman point out that this rear will work for moderate power outputs, but not serious high-performance work. On the unit we had, one of the axles had been replaced sometime during its life, and it had an 8-inch differential cover. This Frankenstein rear end was a perfect candidate for a rebuild, one that would not break the bank, but one that would not use questionable salvage yard parts, either.

Price Breakdown
Master Power 11-in. drum brakes	$495.00
Eaton Posi	$493.12
Yukon ring & pinion	$199.91
Yukon master overhaul kit	$118.92
Yukon alloy axles	$114.95 ea
Axle bearings and seals	$10.48 per side
TOTAL	$1,557.81

Some may wonder why build an 8.2 rather than an 8.5-inch 10-bolt or even a 12-bolt. Have you tried finding a 12-bolt at a swap meet lately? And as for the 8.2 vs. the 8.5 build, simply put, that's all we had under the car, so we built what we had. That's $1,500 for a rear end that should hopefully see a good 20 years of service. That's worth it. Just don't take it out to the track and try and run a 600hp engine with slicks. That's not what it was built for.

If you happen to know the exact year of the differential you are re-building, the Chassis Service Manual is a good book to have as well. But compare the price of one of these "year specific" manuals to that of the Allen & Lyman book: $29.95 vs. $100.00 for the GM book.
If you happen to know the exact year of the differential you are re-building, the Chassis
After disassembly and a few hours of cleaning and de-greasing with a brush, we repainted the housing and tubes at Harrison's Restorations.
After disassembly and a few hours of cleaning and de-greasing with a brush, we repainted t
I used Rustoleum gloss black purchased at a local hardware store to spray the tubes and housing. Not sure if I will do that again. The Rustoleum took a couple of weeks for the paint to really harden. Next time I will go with Por-15 or have it powder coated.
I used Rustoleum gloss black purchased at a local hardware store to spray the tubes and ho

Before getting started, let's run down the parts that are going into this build. The Yukon Ring & Pinion (PN YG GM8.2-355) is a standard 8.2 3.55 gear ratio that is made of 8620 steel. We decided to go with middle of the road gears like the 3.55s, though these diffs were fitted with up to 4.11s from the factory. When used with an overdrive tranny, the 3.55s will be highway friendly, as well as giving significantly more torque multiplication over more pedestrian ratios like a 2.73 or 3.08.
Before getting started, let's run down the parts that are going into this build. The Yukon
Yukon Master Overhaul Kit (YK GM8.2) is for '64-72 GM 8.2-inch 10 bolts. Included in this kit are Timken carrier bearings and races, pinion bearings and races, a pinion seal, a complete shim kit, ring gear bolts, a pinion nut, crush sleeve (if applicable), oil baffles, and slingers (if applicable). Also included are thread locking compound, marking compound with brush, and gasket.
Yukon Master Overhaul Kit (YK GM8.2) is for '64-72 GM 8.2-inch 10 bolts. Included in this
The axles used are (PN YA G1255802-SH). The 8.2-inch axles are 30N-inches (2.780-inch hub) and 28 spline count. On the left is the OE axle we pulled, and on the right is the new Yukon axle. Notice the Yukon axle diameter is a bit larger than that of its OE counterpart...
The axles used are (PN YA G1255802-SH). The 8.2-inch axles are 30N-inches (2.780-inch hub)

...and also the hub of the Yukon axle (right) compared to the OE hub is thicker as well. The Yukon axles are 20-25 percent stronger than OE due to their increased size. In some cases, it may not be necessary to buy new axles. In this case, the original axles were showing extreme wear where the bearings sit.
...and also the hub of the Yukon axle (right) compared to the OE hub is thicker as well. T
Forget having a peg leg wheel-the Eaton Positraction unit (PN EAT19603) uses heavy-duty internals and carbon fiber clutches for a strong, long-lasting unit. As an added bonus, the Eaton unit is also rebuildable.
Forget having a peg leg wheel-the Eaton Positraction unit (PN EAT19603) uses heavy-duty i
Finally, the Master Power 11-inch rear drum brakes (PN DR1700K) are an alternative to a pricier set of discs for 10- and 12-bolt GM rear ends ('64-77 GM mid-size cars and '67-81 Camaro and Firebird). There is no need to change the master cylinder or proportioning valve, and all components come pre-assembled on new backing plates. You must have 3K-inch offset wheels and use 14-inch or larger wheels to clear the drum.
Finally, the Master Power 11-inch rear drum brakes (PN DR1700K) are an alternative to a pr

It would be impossible to show how the pinion gear looks installed in the housing, so we included a photo with the pinion bearing spacer (aka crush sleeve) and bearings...
It would be impossible to show how the pinion gear looks installed in the housing, so we i
...prior to installation.
A great aid that comes with this kit is the instructions. Yeah, instructions. We realize that men are not supposed to read instructions, but how else would we get the pinion preload numbers and torque specs for the ring gear bolts? The instructions included are actually user friendly and easy to understand. That's a bonus for sure. Not to mention, Randy's Ring and Pinion has a great tech line with techies who actually help you solve problems.
A great aid that comes with this kit is the instructions. Yeah, instructions. We realize t

After the pinion gear, bearings and crush sleeve are installed, pinion bearing load is checked with an in-lbs wrench. Save the original pinion shims in order to help determine pinion depth.
After the pinion gear, bearings and crush sleeve are installed, pinion bearing load is che
The instructions call for 12-15 in-lbs of pre-load the 8.2 differential using a new pinion gear. The easiest way to check this is to rotate the pinion nut with the torque wrench. Double check the torque specs after the bearings have set. Also we used red Loctite to lock the pinion nut in place.
The instructions call for 12-15 in-lbs of pre-load the 8.2 differential using a new pinion
At first we were alarmed when the ring gear didn't seem to fit on the carrier. Our technician at Randy's told us this is normal. The ring gear is supposed to fit snugly. One way to install the ring is to lube the inside of the gear where it fits on the carrier, or by placing the ring gear in an oven with a temp no higher than 187 degrees. This will help it slip on. It's normal to have to use a rubber mallet to tap the gear into place. Just don't use a metal hammer.
At first we were alarmed when the ring gear didn't seem to fit on the carrier. Our technic

The torque specs that the instructions call for are first 55 then 60 ft-lbs for the ring gear. Red Loctite is used on these bolts as well.
The torque specs that the instructions call for are first 55 then 60 ft-lbs for the ring g
When installing the carrier and gear, we saved the original shims as a starting point for backlash measurement. Sometimes setting backlash is a trial and error process. In our case the original shims were too tight a fit, so we used the shims supplied in the kit to get the backlash properly set.
When installing the carrier and gear, we saved the original shims as a starting point for
Setting the backlash requires that the pinion gear be immobilized while the ring gear is rotated back and forth.
Setting the backlash requires that the pinion gear be immobilized while the ring gear is r

Moving the ring gear towards or away from the pinion gear centerline helps determine the amount of rotation backlash and meshing of the gears. We set the backlash in the rear end to .003-inch, which is on the tighter end of the spectrum.
Moving the ring gear towards or away from the pinion gear centerline helps determine the a
Once the we believed we had the proper backlash set, we used gear marking compound to check the pattern wear on the teeth of the ring gear. There are about 18 different illustrations in the instruction booklet that deal with acceptable wear patterns. Needless to say, we won't include those in this article. As you can see the gear wear pattern on our ring gear is as close to center as we could get it, which, according to the instructions and Randy's book is acceptable.
Once the we believed we had the proper backlash set, we used gear marking compound to chec
After that, the axle seals and bearings went in.

The Master Power backing plates and then Yukon C-clip axles are installed next.
After the axles were clipped into place, we sealed up the differential using Grade 8-bolts. That might be overkill on our part, but Harrison insisted.
After the axles were clipped into place, we sealed up the differential using Grade 8-bolts
Finally we used Royal Purple 75w-90 gear oil and filled her up. Follow the direction included in the instruction booklet for the proper breaking procedure of the new ring and pinion
Finally we used Royal Purple 75w-90 gear oil and filled her up. Follow the direction inclu

SOURCES
Royal Purple	Yukon Gear & Axle 8-88/-905-5044 www.yukongear.com
Harrison's Restorations	Randy's Ring and Pinion 8-00/-347-1188 ring-pinion.com
Master Power Brakes 254-1 Rolling Hills Rd. Mooresville NC 28117 704-664-8866 www.mpbrakes.com