Hey Guys... need your help! I started hearing a knocking in my left front end and I jacked up my car and check my ball joints pushing up and pulling out and its tight with no movement. I then did the left and right test and i had some movement. I don't think its my ball joints because I do not see movement there however I do see alot of movement on the piece that is attached to my tire rod. When i pull on it I see it moving the steering wheel etc.I see it moving in and out of the boot closest to the car. What is this part b.c I cannot figure it out in the book. Also, is it easy to replace. Ifso cansomeone enlighten me! Iwill any info you can give me!

Thanks

Chris