HindsightKen Hunter, via CarCraft.com: I have a '71 Chevelle, and now I am looking to do the rearend. Right now, I have a 10-bolt, one-tire-fire with 3.73 gears, and I want to put a 12-bolt posi with 4.10s. I found a '72 Buick Riviera in a junkyard with a 12-bolt rearend for $180, but I noticed there was a weird-looking rear axle yoke I have never seen before. Can I take that 12-bolt out and put it in my Chevelle? Would I have clearance and backspacing issues? Can I put the same wheels and tires on with no problems? What are my options?
Jeff Smith: The '72 Buick Riviera is what GM calls a B-body car, which is the next-size-larger vehicle in the GM scheme compared to a Chevelle that is referred to as an A-body car. The rear axle assemblies for the B-body cars are not the same as for the A-bodies and do not interchange. Worse yet, the 12-bolt you refer to is an odd-ball housing that does not share internal components with the typical Chevelle or Camaro 12-bolt, right down to the oddball pinion yoke. So this rear-axle assembly won't interchange on several levels.
The question then becomes whether to attempt to build up the existing 10-bolt or step up to a the stronger but more expensive 12-bolt. The answer lies in how much power you plan to make. If your current combination is a small-block that makes less than 450 hp, then the current 8.2 10-bolt would probably be sufficient. You mention that it's a "one-legger", which can be cured with a performance limited-slip differential, also called Posi-traction, which was GM's term for a limited-slip unit. The good news is there are two limited slips, including an Auburn cone-type and a clutch-type that is similar in design to the original GM unit. We researched the Drive Train Specialists (DTS) catalogue and found a U.S. Gear clutch-type posi for $385.02 (PN US01-082728) that would work fine. DTS also offers several Auburn limited slips including PN AU5420108 for $363.00.