It's important to put it back together just as it is now. Any tighter and it's overhaul time, at least a total disassemble to replace the pinion sleeve. First off, I clean the yoke, the nut and the pinion very well. I then index the three with a paint line from the center of the pinion, across the nut and onto the yoke. Remove the nut and yoke, do your repair, and put the yoke back exactly where it was. Tighten the nut down until it snugs up and then tighten it until the paint marks line up just as they did before disassembly. Easy as that,
Scott
