What spline would a 9" Ford rear have from a 1957 Ranchero, 29 or 31? I need to change the ratio but before I buy another center section it is alot of work to pull an axle. Thanks for any advice.
Probably a 28 spline. You can tell by the bolts holding the backing plate on. Read the first paragraph here; Click here: Ford nine inch differential cases + ReadGenerally most cars received the small axle bearings and 28 spline axle shafts. Exceptions to this were the ultra Hi performance Boss 302’s, Boss 429’s, 427’s, 428 CJ/SCJ and the 429 cars which received the 31 spline carriers and axle shafts. Some of the heavier cars like the Galaxies also received the larger wheel bearing housings.The trucks varied more, early half ton trucks got the 28 spline axles and carriers, while sometime in the early 70’s the switch was made to mostly 31 spline axles and carriers for most trucks. Most of the later trucks also received the larger axle bearings housings.One exception to this was the Bronco’s from 1966 to 1977, they stayed with the 28 spline units. A small bearing housing can be differentiated from a large bearing housing by the size of the nuts and thread used to retain the brake backing plates to the housing, the small bearing housings use 9/16 socket size nuts with 3/8” fine thread, while the larger bearing use 11/16” socket size and 7/16” fine thread. Gross Vehicle Weight ( GVW ) would determine which axle housing many cars and trucks received. Generally most cars received the small axle bearings and 28 spline axle shafts. Exceptions to this were the ultra Hi performance Boss 302’s, Boss 429’s, 427’s, 428 CJ/SCJ and the 429 cars which received the 31 spline carriers and axle shafts. Some of the heavier cars like the Galaxies also received the larger wheel bearing housings.The trucks varied more, early half ton trucks got the 28 spline axles and carriers, while sometime in the early 70’s the switch was made to mostly 31 spline axles and carriers for most trucks. Most of the later trucks also received the larger axle bearings housings.One exception to this was the Bronco’s from 1966 to 1977, they stayed with the 28 spline units. A small bearing housing can be differentiated from a large bearing housing by the size of the nuts and thread used to retain the brake backing plates to the housing, the small bearing housings use 9/16 socket size nuts with 3/8” fine thread, while the larger bearing use 11/16” socket size and 7/16” fine thread. Gross Vehicle Weight ( GVW ) would determine which axle housing many cars and trucks received. Generally most cars received the small axle bearings and 28 spline axle shafts. Exceptions to this were the ultra Hi performance Boss 302’s, Boss 429’s, 427’s, 428 CJ/SCJ and the 429 cars which received the 31 spline carriers and axle shafts. Some of the heavier cars like the Galaxies also received the larger wheel bearing housings.The trucks varied more, early half ton trucks got the 28 spline axles and carriers, while sometime in the early 70’s the switch was made to mostly 31 spline axles and carriers for most trucks. Most of the later trucks also received the larger axle bearings housings.One exception to this was the Bronco’s from 1966 to 1977, they stayed with the 28 spline units. A small bearing housing can be differentiated from a large bearing housing by the size of the nuts and thread used to retain the brake backing plates to the housing, the small bearing housings use 9/16 socket size nuts with 3/8” fine thread, while the larger bearing use 11/16” socket size and 7/16” fine thread. Gross Vehicle Weight ( GVW ) would determine which axle housing many cars and trucks received.