WHAT IS THE CROSSMEMBERS PURPOSE?
Which thing are you calling a crossmember. Some of them hold major systems in place like a transmission. Some may be braces used to keep the car from shaking. What car and where is it located?
It can also be called a sub frame or if your a Mopar man called a K member, it bolts across the front unit body. The lower control arms attach to it and may support the engine and power train. It also isolates vibration from the passengers. In some cars like the Taurus you can unbolt it a drop the entire engine in trany out the bottom of the car