BTW Tony,

i already changed all the bushings. the car doesn't bottom out, but it is lower than the picture on the owner's manual..I never haul loads in the back (except my mother in law on sunday mornings). When i changed bushings and took out rear springs, I just wasn't very impressed with their "springiness" (if thats the right word).

At 170K I would suspect the Trailing arm bushings for your saggy butt. If that is your symptom.

I think many people confuse the saggy bottom with a Spring problem.

I too recomend the IPD heavy duties. see how my car sits in my Profile with new Bushings and new Overload Springs.

My sag was Bushings Not Springs. I had a very busy weekend on a Saturday I pulled the axle down and did the springsThe car sat basically the same, On Sunday I didi the Bushings. That did the trick.
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'75 Jeep CJ5 345Hp ChevyPwr and two motorcycles: it wasn't Volvos safety , it was Longevity that sold me

Nothing complicated about this, as the springs fatigue, the car gets lower. The spring 'rate' does not change as much as the ride hight does.

Look at your car in profile and compare it to an old picture of a new Volvo (like on the front of an old owner's manual). Even if it has settled an inch or so in a decade, that is not necessarily a problem unless you bottom out on bumps.

Unless the car has held very heavy loads for extended periods (as is commonly done to Volvo wagons) then it is unlikely that the springs are tired.

When the springs are worn out the car will sag in the rear. I have had good luck so far with my heavy duty IPD rear springs. They are not too harsh and respond very well to heavy loads.