Do I need new bolts to install this?

Reuse your existing knuckle bolts if they're in good condition. If any are stripped or damaged, you'll need replacements rated for your vehicle — check your service manual for torque spec and bolt grade.

Can I press this onto my old axle shaft?

This assembly is a complete unit; the axle shaft passes through the bearing cartridge. Before install, inspect the shaft for scoring or corrosion where the bearing rides. Light surface rust is fine, but deep pitting or wear will cause premature bearing failure — replace the shaft if needed.

What if the wheel still has play after I install it?

Loose play usually means the knuckle bolts weren't torqued correctly or the axle nut is under-tightened. Remove the wheel, grab the tire at 3 and 9 o'clock, and test again. If play persists, verify all fasteners are tight per your service manual, then test-drive before troubleshooting further.