Hi, I checked my tie rod end just now. When I grabbed the left and right of the tire and rocked the tires, the driver side was absolutely tight but I could see noticeable movement on the passenger side. It's very small but noticeable. So I wonder if there's any way to measure that free play and how much is too much? Thank you very much!

 

Any noticeable play is bad on a tie rod end, its kinda like telling you its on its way out.

 

As auditech stated, any play is too much play, but also when buying a new one here are some tips... don't get deutscheparts brand tie rods, theyre completely horrible, try to get either original audi tie rods, or if need be get a moog brand tie rods. Also since tie rods control alignment, you need to get the car a new alignment, so go somewhere with a hunter laser alignment machine, and test drive it after theyre done aligning it, sometimes they dont do a good job at all (no one knows this better than me) lol. good luck