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Rears already in the car just swapping gears

What ratio and brand gears are you swapping? Dana 60,(non late model Strange brands) use shims on both ends of the pinion gear and the ring gear carrier or spool. Dana has a factory spec for pinion bearing preload with no seal in place the requires you to take the measument with the pinion gear pointing straight up in the air, not 90 degrees to the floor or Earth You need to take the rear end out of the car to get that measuremnet accurate One other thing is the carriers or spools have at least two different ones depending on the gear ratio, 3xxx carriers work with 3.54,3.73, 4.10 and some brands of 4.30 ratio. The 4xxx cariers are used on the 4.56 and up ratio, you can use two pry bars to remove the carrier but you must maintain the carrier bearing preload as well as the backlash You will need a dial indicator to measure the backlash and a way to measure or insure that you get the pinion depth correct also In other words they're a pain to set up properly, not easy like the 8 3/4 are

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)