Originally Posted by jimfulco
That refers to the different ranges of gear ratios used with each different carrier. Lower series number carriers are used with lower ratios because lower ratios have larger (in diameter) pinion gears, and that means the ring gear (and the ring gear flange) has to be farther to the left of the pinion centerline.
The ratio range of each carrier series varies with different rear end designs. In other words, just because one changes between 2.56 and 2.73 doesn't mean they all do. They don't, generally. Some don't even have a 4-series carrier.
Correct and it really is a crash to most who had grand illusions of just a simple upgrade to their ride. GM and Chevy had specific standards for weight ratio on their types of rides. For example, some camaroes came with a 10 bolt and others came with the 12 bolt. This is because of the engine and class design of this model when released. Thus, your transmissions and rear ends where matched tothe HP rating of the engine offered in each series released. Three choices of camaroes, three drive line packages offered.
Some had the momas' ride, got it as a first drive in school. Thought it could be beefed up in the engine, forgot about the final drive. They go to upgrade, so they thought, the rear end, only to find there is three options in the upgrade of the third member, what a bummer! These are the ideo-thoughts of the engineering departments. They do this to force the consumer into purchasing the upgrade at the show room floor. Ching-ching! Sorry......