Before diving into the details of this 8.2-inch 10 diff build, we figure we should address a couple of questions that are sure to pop up. First of all, the 8.2-inch 10-bolt rearend came in Chevy and B-O-P (Buick-Olds-Pontiac) versions; for our purposes, that means it was found in '62-67 Chevy II/Novas and various Novas, Chevelles, and El Caminos through the '72 model year. Question two, which follows quickly and more vehemently, is, "Why would you build one of these things?" So we'll explain the why and what we did to make this thing a viable dragstrip diff.
Our first order of business, of course, was to disassemble the 8.2-inch 10-bolt donor rear
The why of this story follows the idea that it's cheaper to build up what you already have than to buy something else. Would a 12-bolt or a 9-inch be stronger? Absolutely, but a full new replacement setup for our subject '67 Nova would cost at least $2,000. We did find a few used 8.5-inch 10-bolts and 12-bolts during some online searching, but not many-and they were of indeterminate quality. Someone looking to make this swap with used parts would have to factor in the costs of a rebuild and retrofit in addition to whatever was paid for the core diff.
Dave Stoker had all this in mind when it came time to rehab the rearend in his 11-second '67 Nova, a car that gives off no external evidence of its dragstrip prowess. When it comes to cost, Stoker tells us that a core 8.2-inch 10-bolt fetches about $150, if not less, on the open market. Stoker certainly had cost considerations in mind, but he was also looking to keep a Nova rearend in his Nova, as well as maintain its sleeper persona-right down to its bantamweight diff.
Ironically, the diff that needed replacing was the victim of a faulty posi unit, not the small-size differential itself. With this in mind, our first move was to raid the Eaton catalog for PN 19603-010, which is a limited slip differential for '64-72 Chevrolet 8.2-inch 10-bolts with 28-spline axles and 3.08-or-steeper gears. Obviously, we wanted both wheels a-turnin'. On the other hand, Eaton posi units come filled with forged gears and carbon friction discs that will handle the 11-second abuse we'd be throwing at it.
Our second call was to Randy's Ring & Pinion. If you call Randy's for tech support, you'll probably be talking to Terry Burg, as we did. In short, we looked to upgrade every piece we could. The Yukon Gear ring-and-pinion set we chose (in the Nova's original 3.36:1 ratio) is made to be stronger than OEM gears while running as quietly as a stock set. The 1541H steel axles we chose are 25 percent stronger than OEM pieces, according to Randy's. We also ordered a master rebuild kit, which comes with Timken bearings to ensure strength and durability.
With the axles and ring carrier removed, Galloway proceeded to the pinion yoke. If you don
Burg went a step further, strongly suggesting we run a rear girdle rather than a stock cover. "The higher the horsepower level, the more it wants to shoot a bearing cap out the back," he explains. "And this is a small ring-and-pinion with small bearings and carriers." The cover Randy's provided reinforces the bearing caps against just such an occurrence. "It's one of the best things you can do with these small rearends," Burg tells us.
Of course, all these high-grade parts can go for naught if a rearend isn't properly set up, and that's where Don Lee Auto Service comes in. Don Lee tech Rick Galloway has set up more than a few diffs, many of them in heavily abused off-road vehicles. The bottom line here is to take your time and set up the gears correctly-it's the best way to ensure longevity for any rearend.
So what did we get for our efforts? First of all, Stoker reports that this rearend is indeed quiet, a testament to the gearset quality and the professional setup. But more importantly for our purposes, we of course took a trip out to Irwindale Speedway to test our handiwork and saw a nice drop in 60-foot times from a not-too-shabby 1.64 to an even better 1.565. But will this diminutive diff live? We'll let you know, since we've got more straightline fun planned for this slick Nova. In the meantime, check out the highlights of this 10-bolt build.
Assemble an 8.2-inch rear that can survive in an 11-second Nova.
It takes less power to move a small ring-and-pinion. Use quality parts, set it up correctly, and reinforce the carrier bearings, and it will survive.