So I noticed that I had about a ½" sag on the passenger side in the rear. Enough of a sag that I could see it with the naked eye without taking a tape measure to it. So I assumed that I had a bad coil spring OR a failing coil spring. Since I had never replaced the rear struts I thought I might as well go ahead and do that. So I bought a quick strut....however that didn't correct the sag? In fact I noticed I have a ½" sag from side to side (front tire compared to front tire and rear tire compared to rear tire) and about a ¼" inch difference from front to back on each side. So if its not a bad coil spring what else could cause a noticeable sag like this? Bad sway bar? Something else? But if its the rear sway bar why would I also have a sag in the front compared side to side?

 

Sounds like you only replaced one quick strut?
It's highly recommended that both struts on the same axle (if not all four) be replaced at the same time with the same make and model, even if the opposing strut on the same axle seems good. Ride height varies with wear and differs from one coil/strut manufacturer to another. Also, a worn front strut can affect the ride height of the rear, and visa-versa. For example, if the right front strut is worn that corner will ride lower, thus the opposite corner (left rear) might ride higher. The sway bar shouldn't make a difference since it's not supporting the weight of the car. I assume you're using the same tires and pressure side to side, front and rear? and weight distribution is equal?

 

Nope.....replaced the rear struts.....in a pair---same time, same make, same model, Detroit Axle brand. I have not replaced the fronts. Ride height is 29" from ground to bottom of wheel well on rear driver side, 28¾" from ground to bottom of wheel well on front driver side, 28½" from ground to bottom of wheel well on rear passenger side, 28¼" from ground to bottom of wheel well on front passenger side. So ½" from side to side and ¼" from front to back. Ohtsu FP7000 tires all the way around with approx. 34 lbs of pressure in them. Only weight is a speaker box in the back with two 10" Kickers and a Kenwood amp and myself (I weigh approx. 198 lbs on the driver side of course, which consequently is the higher side).

I will say this we jacked up the rear and took the tires off to look at and disconnect the sway bar and after assembling everything (including the sway bar) the sag seemed to disappear. Although this has happened before after jacking up the rear the height seems spot on, but then after driving it sags again in a day or two? This is very puzzling to me.....