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http://www.kevinstang.com/Ninecase.htmHousings and Bearings, etc.
This is a new section with some recently obtained specific information I have gathered on the types of bearings and housings used by Ford. For the nine inch there are are two bearing sizes used for housing ends, the smaller eight inch used just one. However, for the nine inch (as assembled by Ford)there are 3 different bearings- one small and two large. The two large are the same size ( I.D. / O.D specs), but different types of bearings- one is the traditional sealed ball bearing, while the other is the oil bathed roller bearing and race type.The eight inch and most nine inch housings used the small bearing- including the 31 spline CJ cars, Mustang Hi-performance etc.. This bearing was of the sealed ball bearing type, # RW207CCRA (specs: 1.378" I.D., 2.8246" O.D. by 0.8449" width). Early Galaxies and Broncos and some mid 70's Torinos used the large type sealed ball bearing, which meant they had a large tube housing end, bearing # 88128-RA (specs: 1.5312" I.D., 3.1496" O.D. by width). The second type of large bearing (roller type) was used in later pickups and larger Ford cars, bearing # A20 (specs. 1.530" I.D., 3.1530" O.D.), the seal was on outside of bearing. Because of the two different size bearings used in the 9 inch, there are also two (actually three) different backing plate mounting patterns as well. The standard small bearing has an approximately 3 1/2" (horizontal)by 2" (vertical) pattern with 3/8 inch mounting hole diameter, while the large bearing is 3 1/2" by 2 3/8" respectively with 1/2 inch hole size. Some of the mid 70's Torinos used a slightly different plate with a spacing of 3 9/16" by 2" respectively with 3/8" hole size. Good news for restorers and rodders out there is that there are adaptor bearings available to ease the swapping of axle shafts and housings that would have originally been potential problems. There are bearings made to swap the larger 31 spline shafts that may have been shortened into small bearing housings (spces- 1.531" I.D. by 2.834" O.D.)-it is available from aftermarket suppliers. I think there is also a bearing that will do the swap the opposite- swap typically small bearing shafts into a large bearing housing, the info I have found is that the BCA 511004 will do this, haven't tried it myself yet, but is has the correct 1.378" I.D. by 3.1496" O.D. .
Another area of concern when swapping axle housings into earlier Mustangs (65-66 models especially)is the diameter of the outer axle tube.Note the taper on this 8" 65-66 Mustang housing, a smaller U bolt and lower shock plate were used originally with these cars.The HIPO 289 cars were the only 65-66 Mustangs to recieve factory 9" axles, the tubes are tapered as well at the end to utilize the same lower shock plate as the regular 65-66 Mustangs.
JohnB