kanadian

I need to replace one of my control arms but I am confused as to which part to order.. My confusion stems from the parts description online.. For example: front lower/upper forward/rearward. The one I'm interested in is front left with the ball joint facing up and the nut goes on from the top. Which is this? And how do i differentiate whether its rearward or forward or w/e? 2002 c240 red auto

slammer111

The "upper arm" is the one towards the front of the car, and is made of aluminum (unpainted/grey colour). The "lower arm" is towards the rear, and is made of steel (usually painted black). The MB nomenclature is confusing as hell unfortunately. Definitely feel your pain on this one - I was just as confused when replacing parts on my own car.

Each front wheel is attached at the knuckle by 3 parts - upper arm, lower arm, and outer tie rod (which is attached to the inner tie rod which is then attached to the steering rack).

To answer your question, the one you want is the "lower arm". Those ones seem to be the first to die in many cases. It is highly suggested that you replace the lower arm on the other side as well, as it is probably about to die soon. On my car, both lower arms went (ball joint failure) within 6 months of each other. Ended up having to pay the indie twice.

RWDlifer

I'm actually doing the control arms today, plus rack bushings, tie rods and bearings. The upper arms have down facing ball joints and vise versa...

kanadian

Thanks guys I appreciate it. I shall replace both side as a precautious measure