Ok, the pre-load on used bearings is zero with NO play
First, hold onto one of the output shafts and the ring gear at the same time. Try moving the output shaft while holding the ring gear from moving. Any play? If so, how much?
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Procedure to set ring/pinion backlash and diff bearing pre-load.
- clean side seal nut threads so they are very easy to turn in and out
- make sure ring, pinion and bearings are scrupulously clean
- keep the gears clean and dry
- very lightly oil the diff bearings
- short side seal runs removed from output shafts
- run the side seal nuts in until they are "snug" with a "little" bit of backlash in the gears
- if freeplay is tight or loose, loosen one side before snugging the other again to move the diff carrier one way or the other
- firmly attach a the base of your dial gauge so that the gauge will work perpendicular to one tooth on the ring gear
- use two screwdrivers to try and move the diff carrier side to side. There must be NO play.
- gently rock the ring gear forward and back to get a backlash reading
- carefully move the diff carrier one way or the other by first loosening one nut and snugging the other. Always double check for diff carrier play after any adjustment.
- everything perfect? No diff carrier play and backlash correct?
- mark your side nuts
- remove one and coat the threads with a non-hardening and non-setting sealant like hylomar or Permatex Aviation Gasket Maker #3
- reinstall the nut, snug up to your mark
- repeat for the other side
- double, double check there is NO play if you use screwdrivers to try and move the diff carrier side to side.
- double check the backlash
All good? At this point I would also do a contact pattern check. You can skip this if the transaxle was known good before.
There must not be absolutely any play in the diff carrier bearings. Better a slight amount of pre-load than any play whatsoever!!!
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Apply a light smear of grease to the side seal lips. Very lightly apply non-hardening sealer to the side seal run's o-ring and fit it on the output shaft. Very lightly apply non-hardening sealer to the o-ring well on the side seal run. Gently push the side seal run in place being careful not to damage the seal. Get a piece of tubing and use a hammer to give the tubing a sharp rap to make sure the seal run goes all the way home.
Except for half shaft shimming, you're done.