300ZX Wheel Sags Right Rear

I bet you have a broken spring.

No wheel imbalance. No signs of fluid leakage.

jeez man just jack it up and see if part of a spring falls out

I plan to once I have the time to look at it. But, if the spring does fall out I'll send it to you as a gift.

I had a shock that failed that caused one side to lean really bad. The suspension was also really bouncy. Check for that, but more importantly, just do like FrozenZ said and just jack up the damn thing already!

Rear sub-frame bushings may have failed. Rear shocks and springs are weak. Will probably need to replace all of the suspension components. Was looking at the KYB gas shock kit because that seems to be all that's available for this car. Not my first choice of shocks. Are the Tokico Illumina 5-way adj. (BE2740) shocks still available for the Z31? Old tech notes also say the BE2740 will not fit models with adj. rear suspension.

You should be able to find the Tokiko's but for sure I have seen the Bilstein's out there. I think the Tokikos should be around still too. I have to say the KYB's have done very well on my car, I put them in 1990, I had one issue with them about 2 years later and they replaced under warranty so 20+ years with no issues. Now if I could find the bilstein's around I would use those, but it depends on your tolerance for stiffness.

Looks like the Tokico rear shock is BZ4005 and they appear to be discontinued. Even if I did find one, I think they need a non-adj strut insert.

Those seem to have gone by the way of the dodo bird so I think your choices are the KYB's which are solid and will most likely be the last shocks/struts you need or the Bilsteins which are also super high quality and will be a litle bit stiffer.

Bilsteins on their own in the rear are OK, I recommend them. When you combine Bilsteins and poly subframe bushings it starts feeling kinda racecar for a daily, especially if you live somewhere bumpy/pothole-y.

I would bet, the KYB's with poly bushings and bigger rear and front sway bars is enough handling for me. I drove my car down to LA from SF (about 400 miles) and I wouldn't have wanted it to be any stiffer