The 8.5-inch 10-bolt axle required to bolt directly into a '67-'69 Camaro or Firebird can
`The first-generation Camaro has achieved rock-star status at this point. We saw something like 15 of them in various displays at the '05 SEMA show in Vegas. But if the mail and the people we encounter on the road are any indication, there are still plenty of these cars in the hands of grassroots enthusiasts. Even if you weren't fortunate enough to secure one before the Barrett-Jackson boom, there are still loads of formerly junk '67-'69 Camaros out there to resurrect, so long as you're willing to do a whole lotta welding.
That said, there's still the matter of actually building the car to do what you intended in the first place: go fast. But if you find yourself getting annoyed at the prices complete cars are fetching, wait til you see the coin needed to score key parts and pieces. For example, any early F-car worth its salt ought to have a 12-bolt, right? Good luck finding an original, and when you do, it'll likely take north of $500 just to get a core that still needs to be rebuilt. Sticking with the stock 10-bolt isn't much of an alternative. It's a wimpy 8.2-inch unit, and really isn't worth investing in since you're going to need gears, a limited slip, probably new axles, and so on, and you'll still have to fret about grenading it every time you launch. Of course, the aftermarket can offer you a choice of a brand-new bulletproof 12-bolt, 9-inch, or Dana 60 ready to bolt in, but it'll take in the neighborhood of two Gs to get one. If you can afford it, the new heavy-hitters are great, but if not, we have an alternative.
The 8.5-inch 10-bolt axle hadn't reached production during the era of the first-gen Camaro but soon after became a staple for GM cars. This stronger 10-bolt was intended as a "corporate" axle to be used across GM lines, and it had to be fairly strong as the 12-bolt was going away. Chances are you've abused one of these axles before and probably didn't even realize it, since it was used in pretty much every '71-'81 F-car, as well as '73-'77 A-body cars, '71-'76 B-bodies, heavy-duty '77-'96 B-bodies, '84-'87 Turbo Buicks, and countless scores of 12-ton GM trucks among others. But the application that matters most to our story is the '71-'74 Nova and other X-body clones. This is the one that bolts right into a '67-'69 F-car, and this is the way we're going to build a stout rearend for a modest investment.
As you might guess from the long list of applications, parts for the 8.5-inch 10-bolt are plentiful and carry relatively painless price tags. There are also several ways to go about building this rear, depending on your needs and budget. We're focusing on an upgraded 10-bolt using a brand-new differential, gears, and 30-spline axles--the same as those used in factory 12-bolts, but check the sidebar for more budget-oriented alternatives.
One advantage to starting with a complete rearend is having the stock axles for reference.
If you know how to set up a rearend, you're ahead of the game. We don't, so we went to Tim
Next, the stripped axlehousing is mounted to a shop vice via a custom plate that Tim bolts
One of the key elements to our buildup is the Eaton heavy-duty limited-slip differential.
The car this axle will go in sees lots of street use and has a fairly torquey small-block,
Once the new bearings are pressed onto the carrier, the differential assembly can be test-
With the differential bolted in place, Tim sets up a dial indicator and checks the backlas
The next step is to "run a pattern" between the gears. This entails coating a section of r
Once the proper gear pattern was established, Tim was able to remove the differential and
An alternative to typical production-oriented crush sleeves (left) is the solid pinion spa
We sealed the cover on our fortified 10-bolt and then slipped in a fresh set of axleshafts
PARTS LISTDESCRIPTION PN SOURCE PRICERearend assembly, 8.5-inch
10-bolt, used N/A Ecology Auto Parts $54.95Eaton heavy-duty
limited-slip differential EAT 19559 Randy's Ring & Pinion
$430.00Yukon ring-and-pinion gearset YG GM8.5-342 Randy's Ring & Pinion
$170.00Set-up kit YK GM8.5HD Randy's Ring & Pinion $87.00Axle
bearing and seal kit AK 1563 Randy's Ring & Pinion $16.00 x2Axleshafts,
30-spline C-clip GM 12398538 Dutchman $235.00Labor: Set up
rearend N/A Moore Automotive $200.00
The Extreme Budget 10-bolt
While the main focus of our buildup is a fairly stout 30-spline 10-bolt, there is always the option of simply freshening a factory-spec assembly, which is still quite durable. Our assembler, Tim Moore, has put together quite a few stockish 8.5 rears for local customers with excellent results, and he has on occasion used a surprisingly high content of used parts. We've already covered the housing needed, but finding a factory Posi-traction diff in a Nova axle is unlikely. However, finding a late second-gen Trans Am or Z28 in the boneyard isn't so tough, and they're nearly guaranteed to have the desired limited-slip diff. Later 8.5 10-bolts found in mid-'80s vehicles usually have the gov-lock-style limited-slip, and these are best avoided as they have a tendency to fragment under heavy power application.
In our local yards, the complete, drum-to-drum passenger car rear axle is only $54.95, and a creative scrounger could probably take out the open diff and drop in the limited-slip from another rear to maintain that price--the big yards don't seem to care as in the end, it's all scrap to them anyway. But even buying the diff separately is still cheap. Tim Moore swears he's set up plenty of used factory gearsets without incident or even noise, owing to the high quality of GM's stuff and the consistency of its tolerances. Throw in a set of fresh bearings and seals, maybe a posi rebuild kit, and you're on your way. Tim also advises that the cross-shaft that mounts the spider gears is a common wear part and is often responsible for reduced clutching of the posi. Dropping in a new one often brings even original clutch packs back to life (though we're hearing they've been discontinued). Obviously, it's up to you to decide which items to replace and which to reuse, but you can mix and match from our price lists to come up with your own recipe.
DESCRIPTION PN SOURCE PRICERearend assembly, 8.5-inch
10-bolt, used N/A Ecology Auto Parts $54.95*Limited-slip
differential, used N/A Ecology Auto Parts $43.95*
Ring-and-pinion, used N/A Ecology Auto Parts $46.90*Set-up kit,
new YK GM8.5 Randy's Ring & Pinion $87.00Posi rebuild kit YP
GM8.5-PC-E Randy's Ring & Pinion $110.31Axle bearing and seal kit, new
AK 1563 Randy's Ring & Pinion $16.00 x2Axleshafts, 28-spline, C-clip, used
N/A Ecology Auto Parts $15.95**Car parts; truck part pricing is
different; core charge applies
`SOURCESDutchman Motorsports; Portland, OR; 503/257-6604; dutchmanms.com
Ecology Auto Parts; Santa Fe Springs, CA; 562/921-9974; ecoparts.com
Moore Automotive; Sun Valley, CA; 818/767-8343Randy's Ring & Pinion; Everett, WA; 866/262-3281;
Ratech; Cincinnati, OH; 513/742-2111; ratechmfg.com
T&D Machine; Carson City, NV; 775/884-2292; tdmach.com
Since there are a few choices of rear axle to be found under the GM cars we're covering in this story, here's a quick visual reference to help figure out what you're looking at the next time you go to the boneyard.
GM 8.5-inch 10-boltThis is what you're looking for if you want to replicate our efforts. T
Chevrolet 8.2-inch 10-boltThis is the rear you're most likely to find under a first-genera
B.O.P. 8.2-inch 10-boltThis axle would probably only turn up in a '67-'69 Firebird, but af