friend of mine has a broken rear spring in her 1997 Legacy wagon. at least, it makes lots of noise and when i grab the spring it's loose - guess that means the spring is broken?

 

i have a pair of 2002 rear WRX springs sitting around and would like to help her out - can i just install one of those in her rear 97 strut?

I would not replace just one. If they are interchangeable, I would replace both to keep things nice and even, at least side to side.

i figure the WRX springs are going to be a good bit different than L model 1997 Legacy wagon springs! i've got both so hopefully they work?

Aren't the WRX springs short? (shorter than regular Impreza springs anyway, which should be about the same as Legacy springs) I thought I read that somewhere, could have been STI springs though.