rear end play

[bonanza7369]

how much free play should there be in the rear end when you turn the driveshaft by hand? This is a 56 ford standard rear end.
How much should the driveshaft move before you feel the rear end engage?

 

[Ole Don]

When new, there was very little play. Maybe 1/4 to 3/8 inch turn of the driveshaft. If you have more, and have no noise, leave it. Change oil and go heavy. 90/140 was my choice, but it was not used in a very cold area.

 

[rotorwrench]

The back lash was set at the .003" to .008" range with the bearing preload within specs. It should remain in this range until the bearings & gear teeth are worn far enough to eliminate the preload and normal backlash. After that, the slop gets worse until it starts making noise due to too much play. If you want to keep running this rear axle you should take steps to see what kind of play and wear it has in there. Parts for these old buggers are getting scarce but if the damage is already too far gone, a person might consider changing it out to something easier to get parts for.

These axle assemblies were the precursor to the 9-inch. The center section generally has to be removed to check them out.

 

[Motorhead6]

To check for proper backlash on the ring and pinion, you have to remove the "chunk" or "pumpkin". The reading is taken by using a dial indicator on a ring gear cog and holding the pinion gear steady. Movement of .010" to .020" is very good on a unit with normal amount of miles on it. Once installed, it will feel like a lot more due to the free play in the various other components in the train such as axle splines, differential planetary gears backlash. The real test for the novice is if there is whining in the rear end while driving, lateral movement in the pinion yoke (not the universal joint), or leaking pinion seal. To just twist the driveshaft back and forth will feel loose sometimes when this can be very normal.