Hi, I am John Mc, a Ford dealer technician.I hope I can help solve your problem quickly and accurately.
Sorry there is not torque spec on the pinion nut. You have to measure the rotational torque before you remove it to get it to the same reading. The way I do it is I mark the pinion nut, the flange and the pinion and count the number of turns to remove the nut and install it the same amount of turns then line up all the marks. If you over tighten you will over crush the crush sleeve and too loose and you will cause problems also. Either way if it is not just right you will damage the bearings over time. I am also posting the Ford procedure to further assist you.
Click here for procedure
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what do you do if you didnt record the original preload reading is ther a general torque spec to tighten the nut
No there isn't. Here is what to do. Use a 1/2" impact and install the pinion nut until the socket stops turning. Do not try to make the gun overtighten it. When the nut makes a major load on the gun stop. Hard to describe but this is the best way. When done you should be able to turn it with your hand and there should be no play in and out. Pretty much watch the socket it will turn at a certain rate, when that rate slows a good bit stop.
Sorry to be vague but this is the best I can explain.