How to know if control arm needs replacement?

This is an old thread, but it's never too late to offer a suggestion.

Here's a tiny bit of advice when working with control arms or ball joints: You need a pry bar, about 2 feet long. Example: link for Craftsman set of 3 on Amazon; about $27 in 2025.

When you need to wiggle the control arm around to insert the ball joint studs into the control arm, shove the 2 foot pry bar right into the outboard end of the control arm where the ball joint mounts. Use it as a lever to help move the control arm up or down to where you want it to be.

Archimedes is your friend ("Give me a lever and a place upon which to stand, and I will move the earth").

Being able to muscle the control arm around makes it a lot easier to get the ball joint studs in without buggering them up. I tend to put the ball joint's bolt in first, and then run the nuts onto the ball joint's studs.