Pinion bearing.

[ford38v8]

Originally Posted by Bored&Stroked

Use an inch-lbs torque wrench if you have one to set the preload.

Or the good ole' spin the banjo with the pinion end in a vice until it "feels right" trick.

I believe the second option to be the most reliable one. I tried the first, and could never get a good read due to erratic jumping of the indicator. I’m told that back in the day, all real mechanics had been born with torque wrenches built into their wrists: “Spin hard with both hands, and the preload is correct when the rotation stops at or just before one complete turn”. So that’s what I did and it worked for me, many miles ago.