First version: Ratio of 4.10:1, teeth = 10/41

Second version: Ratio of 4.08:1, teeth = 12/49

Third version: Ratio of 3.92:1, teeth = 12/47

Fourth version: Ratio of 3.75:1, teeth = 12/45

Fifth version: Ratio of 3.69:1, teeth = 13/48

Production started with a gear ratio of 4.10:1. This ratio was used in all rear axles up until VIN 002643, and additionally, on 002645, 002646, 002647, 002654, 002655, 002692, 002706, 002822, 002833, 002847, 002848, 002855, 002856, 002869, 002897, and 003238. The Factory part number for this rear axle is 112-350-10-00.

From VIN 002644 (with the above exceptions), the ratio was changed to 4.08:1. This rear axle was supplied through VIN 003482. The Factory part number for this rear axle is 112-350-17-00.

From VIN 003483 through VIN 005137, again a different rear axle was used, but retained the 4.08:1 ratio. The Factory part number for this rear axle is 112-350-13-00.

From VIN 005138 through VIN 008909, the ratio was changed to 3.92:1 in the sedans, and 3.75:1 in the coupes and convertibles. The Factory part number for the 3.92:1 rear axle is 112-350-21-00. The Factory part number for the 3.75:1 rear axle is 112-350-22-00.

Note that as the different ratios became available, that any of the cars could be special ordered with any of the available ratios, except the 4.10:1 ratio which was replaced by the 4.08:1 unit.

NOTE: Be aware that rear axles built after Aug. 1965 are not the same as the rear axles built before that time (see End of Life/Break in Production), even though they may have the same ratios. These later rear axles use larger brakes which will not accommodate the 13" wheels, and the body of the differential is different. A quick check is the presence of the ratio stamped on the lower rear edge of the case. Pre-Aug. 1965 differential cases have a flat circular milled surface on the bottom left corner of the rear surface of the case with the ratio stamped on it. (For example, "3/92" indicates the 3.92:1 ratio.) The Post-Aug. 1965 differential cases are completely different and do not have the flat milled spot, and do not have the ratio present anywhere on the outside of the case.

Note that the 3.69:1 ratio was only available in the post-Aug. 1965 style differential. The 3.92:1, and 4.08:1 ratios remained available as well, but also used the later design and are not directly interchangeable with the pre-Aug. 1965 units.

Starting with production in 1961, the wheels were attached to the rear axles with lug nuts. This was eventually changed to lug bolts. On the rear axles with lug nuts, the wheel was "centered" by the nuts. On the rear axles with lug bolts, the wheel is "centered" on the short stub axle, passing through the center of the wheel. The lug bolts just held the wheel to the axle shaft. Cars built before serial number 004524 used the first style with the lug nuts, 004524 and later used the lug bolts. Also see Wheels.