Hi people, I'd like to ask a question regarding the 1999 Dakota Idler Arm. Thanks in advance for any input.
I was hunting for a thump noise on the front suspension when backing and braking the truck and that turned out to be one loose bolt on the UCA bushings axle, fixed, but then I noticed the idler arm has a play on the shaft that bolts to the frame. When shaking the front wheel I noticed the arm moves up and down about 1/16" in the shaft bolted to the frame.
I bought an aftermarket arm to compare and it seems to have a spring built in that place to allow some up and down movement besides turning.
Please check pics. I have a short video too:

https://youtu.be/aNS-zoYEPNw

My question is that up and down movement supposed to happen or the idler arm is bad? The new one allows the same movement and requires about 60 lb applied to it in order to move.
Thanks again.

Spring built in ball joint

Aftermarket Dakota idler arm

Play on idler arm

 

Once I was curious I found out on wikipedia:

Motion-control ball joints tend to be retained with an internal spring, which helps to prevent vibration problems in the linkage.

So that might be the case. I just thought the power needed to compress the spring should be higher but the old stock arm requires about the same as the new aftermarket part so I will take it is still good.

https://en.m.wikipedia.org/wiki/Ball_joint