When ab 8 3/4 breaks................????????

Dartnut said

The original 489 case 3:23 cone sure grip in my '69 Super Bee 440 4 speed blew out the pinion bearing after the crush sleeve failed.
Lots of burnouts with L-60-15s and a good Mcleod clutch didn't help............
Installed a 3:54 Dana 60 out of a rolled '68 GTX, problem solved!

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Probably a front pinion bearing went first causing end play. then crunch. front bearing is the same as 12 bolt.ford 9" but not as heavy as the 742 cases.sometimes pinion nut backs of from driveline vibrations or reusing nut after seal change( seen lots of those in all rearends).paul