Monotube has no spring/adjustments and the large rear spring is maxed out

First time looking under the G. I was pleased to see a previous owner installed Tein Coilovers, But I am very confused as to how to adjust ride height with no spring or adjustments on the mono tube. The large Spring in the back appears to be completely maxed out, will loosening it give me a drop or will it just make the suspension loose? Should/can I get a spring for the mono tube?

 

G37s/370Zs have a divorced spring/damper set up - you adjust ride height with the spring collar, and preload with the damper tube.

If you want it to go lower, adjust the big one on the right so that it moves UP. As you said, if that's maxed out, then that's as high as it will go. You then make the same amount of adjustment on the damper, assuming the preload was set properly in the first place.

You can get a "true" style coil-over for the rear, but since you already have mostly adjustable coils I don't see the reason to.

 

The rear adjustble spring appears to be maxed at the highest lift. I assume turning the collar counter- clockwise and "Loosening" the spring will give me a drop. Thank you!

 

Yep, pretty much! Loosen the top collar and move it away, then slowly move the lower collar until it's where you want. Then lock it up again with the top collar.