The preload is measured with the pinion installed without the carrier. Assemble in this order: pinion shim, inner bearing, crush sleeve, outer bearing, oil slinger, pinion seal, flange, nut. You will need something to hold the flange while tightening the nut because the crush sleeve takes a lot of force to collapse. Tighten the nut until all of the play is out of the bearings then start tightening the nut a little at a time until you get the proper preload. The spec is 16-29 in-lbs so anywhere between that is fine. I try to split the difference. After the pinion is installed then install the carrier and set the backlash. The spec for that is .008-.012 thousanths. Again I try to split the difference. Once the backlash is right then install the axles. I assume you are reusing the ring and pinion and pinion shim so the pinion depth and gear pattern should be right.
Ford senior master tech
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