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Genera info about rearaxles.
"Open" means that it does not have a slip limiting feature, commonly known as a "Posi". Every marque has their own name and design for their limited-slip rear. Pontiacs were "Safe-T-Tracks", Chevrolets were "Posi-tractions", etc. Posi-tractions can be rebuilt and are tunable; the Safe-T-Track is neither. With an open rear, the right wheel always spins when you nail it or on wet/snowy/icy streets. The limited slip rear transfers torque from the slipping wheel to the gripping wheel, and you get more traction up until both wheels break loose at the same time (assuming a healthy and well set up unit). You can upgrade an open diff. to a posi, but you have to replace the entire carrier (or "case"), which ain't cheap. The diameter of the ring gear indicates the strength of a rear -- larger is stronger. The Ford 9" is considered the strongest factory rear. A 12 bolt has a 8.875"? ring and is the strongest passenger car rear that was made by GM. It only came on GTOs in 70-72, and only when equipped with the optional 455 V8 -- however, units from a Chevelle bolt right up. Pontiac, Olds, and Chevrolet all made their own 10-bolt rears. The Pontiac 10-bolt (also used in Buicks) has a 8.2" ring and was the best of the three -- it came on all 389 & 400 equipped GTOs. The Chevrolet also had a 8.2" ring -- it's almost as good and it's much easier to find parts. The Olds 10-bolt is weak with impossible to find parts. The new GM corporate 10 bolt has a 8.5" ring, but never came in an A-body, so the mounts won't match. "I hope I remembered all this correctly" Chris H. |