Rear suspension knock., Searching wasn't helpful. Options

[richee3]

I recently installed TRD coilovers on the Celica to replace the aged stock suspension. The struts weren't totally blown but they weren't great and the springs had to have helper blocks in them, but they were quiet. After lowering, we found that the rear started knocking quite badly. Based on recent threads, I replaced the rear sway bushings with 16 mm with Energy Suspension bushings and the end links with Racing Beat Miata end links. While this cut the knocking down by half, there is still a persistent knock. It only happens at low speeds and seems to be from the right side more than the left, but it isn't strictly on one side or the other. All nuts and bolts have been checked and are confirmed to be tight.

When I searched, the only potential suspects I can find are trailing or control arms or the exhaust hitting the car. I don't believe it's the exhaust since it only happens at low speeds and I've followed the Celica and the exhaust seems stationary. So what are the odds that I need new rear bushings and it didn't become apparent until I was lowered? Anything else I should check? Any help or advice is greatly appreciated.

By the way, I'm intending to replace my rear bushings anyway, I just haven't done it yet. Procrastination is terrible.

[Galcobar]

The problem's actually fairly common. It sparked a few years worth of debate at Celicatech over the exact nature of the bushing, actually, as individuals replaced the arms to resolve that clunk. The All-trac fifth-gen definately used rubber bushings in the suspension arms, but the naturally-aspirated versions apparently used spherical bearings because the suspension movement was somewhat different. As a result, the fifth-gen owners had no choice but to replace the entire arm; well, they could theoretically have pressed out the bearings and replaced them but the cost of two bearings and the effort required made it impractical.

I wrote that how-to because I would see the question of a clunk from the rear suspension come up so often. Due to age it's a more common issue on the fifth-gens than on the sixth. I mention the testing procedures in this thread simply because of the cost of replacing all the possible sources of a clunk.