How to Know When Diff Subframe & Suspension Bushings are Bad

Waking up this older thread. Later this fall or early winter, I'll get under our ST185 and see if I can get a pry bar to check bushing slop, and check those spherical bearing units as well.

I know I want a comfortable, compliant street car (not a track car) regarding suspension firmness. Most poly bushings are a fair amount harder than natural rubber, so I don't want to go that route. That said, Toyota's availability of OEM natural rubber bushings is very, very limited now. Where Toyota OEM is not available, I don't see any other options but poly bushings. The threads I've seen generally don't sound encouraging to me for poly bushings (they are harder, there is move vibration and noise getting through, and they generally don't seem to last very long).

Paul from GT4 Racing said their normal poly bushing hardness is in the 75-80 ShA range, or about 15-20% harder than natural rubber. They can provide poly bushing hardness around 90 ShA for track & racing (just the opposite direction from where I want to go). They can also provide poly bushing hardness around 65 ShA which would be similar to natural rubber. I don't know how that translates into energy/shock absorption differences between natural rubber and softer poly bushings.

Has anyone used softer poly bushings on ST185's and felt they got back to "showroom" suspension characteristics for these cars? And have they been durable (as durable as natural rubber)? If you found sources for softer poly bushings, from where did you get them? And did the source provide all bushings needed for an ST185 (to not be forced to mix & match various kinds and hardness levels of bushings within a single car)?

I'm just not finding this process of sourcing "factory-spec" type of bushings for ST185's easy at all.

93celicaconv":1s6tfwbf said:

Waking up this older thread. Later this fall or early winter, I'll get under our ST185 and see if I can get a pry bar to check bushing slop, and check those spherical bearing units as well.

I know I want a comfortable, compliant street car (not a track car) regarding suspension firmness. Most poly bushings are a fair amount harder than natural rubber, so I don't want to go that route. That said, Toyota's availability of OEM natural rubber bushings is very, very limited now. Where Toyota OEM is not available, I don't see any other options but poly bushings. The threads I've seen generally don't sound encouraging to me for poly bushings (they are harder, there is move vibration and noise getting through, and they generally don't seem to last very long).

Paul from GT4 Racing said their normal poly bushing hardness is in the 75-80 ShA range, or about 15-20% harder than natural rubber. They can provide poly bushing hardness around 90 ShA for track & racing (just the opposite direction from where I want to go). They can also provide poly bushing hardness around 65 ShA which would be similar to natural rubber. I don't know how that translates into energy/shock absorption differences between natural rubber and softer poly bushings.

Has anyone used softer poly bushings on ST185's and felt they got back to "showroom" suspension characteristics for these cars? And have they been durable (as durable as natural rubber)? If you found sources for softer poly bushings, from where did you get them? And did the source provide all bushings needed for an ST185 (to not be forced to mix & match various kinds and hardness levels of bushings within a single car)?

I'm just not finding this process of sourcing "factory-spec" type of bushings for ST185's easy at all.

Click to expand...

FWIW, I LOVE the poly bushings in my convertible. Whiteline in the front control arms, and GT4 on the rear lateral links and knuckles. Very streetable. Now, running stiffer driveline bushings can have a very different effect on driveability.

Update on my situation with the clunking sound coming from the back end when going over slight road imperfections. Had already changed the rear sway bar bushings and rear struts. Rear sway bar links were good. Driver side rear wheel had some movement that I could make happen when rear was jacked up with tires off the ground - and it would sort of clunk. Passenger side moved less and I could not get any sound when I could move it. Was thinking wheel bearings. Tried prying all the bushings in the back - all felt good in my judgment.

Took it to a trusted mechanic. He also felt the change for rear control arm bushings or strut rod bushings to be bad would be "unusual", as well at the rear subframe bushings. He also checked them and felt they were good. He checked the rear wheel movement, then got a second person to assist and from their test, they felt the wheel bearings were fine, with the problem being the spherical bushings on the controls arms at the rear carriers (or knuckles). I took a bit of a risk and trusted his judgment, so I got new spherical bushings and all new hardware (bolts, nuts, washers, rear toe adjusters, etc. from Toyota. The mechanic finished the work late last week and I got a 4-wheel alignment the day following the mechanical work. Result:

Rear clunking is gone. No rattles, shakes, nothing but what feels like a suspension on a car right out of the showroom. Funny thing though is the car pulled slightly left and the steering wheel was slightly off-center right. Given the 4-wheel alignment values (they shop give me the initial and final readings - the initial were useless as the mechanical work would have destroyed the prior alignment work, and the rear toe wasn't possible to change due to being rusted tight, so they left that alone, saying it wasn't out of spec much. Only put 300-400 miles on since the alignment done previous (which involved all new wheels and tires at that time). I put the 4 wheels on in the same locations they were previously too. Didn't have this slight pull and steering wheel off before. Took both front wheels and swapped them side-to-side. That took maybe 70% of the pull and the steering wheel being off center, making it closer to spot on. Then did the same from the 2 rear wheels. That got maybe an additional 15% better. Very slight off-center right yet, and the pull to the left is gone - tracks straight and tight now. The tires, by-the-way, are considerable wider than factory originals, so I know these wide tires tend to amplify this kind of thing a bit. So I'm not sure if the few miles put on when the rear was not adjustable (and did the shop offset the front alignment at the time so as to cancel the effect out, but caused some tire wear that, now with the alignment spot on, that slight wear distortion is causing my situation now? Or did the alignment shop simply not have the steering wheel centered when they made their adjustments?

Anyway, with the wheels on the way they are now, I'm perhaps just a bit to anal on the steering wheel position - it is so close to being centered. And the suspension feels like new and very quiet again. So I'm glad I didn't take out additional bushings to try to fix something with them that wasn't a problem. Those old natural rubber bushings, being 29 years old, they are still pliable and doing what they should be doing. I'm amazed at how much of a difference changing those spherical bearings made, given how little movement they had - but they sure made some clunking noise when driving on uneven pavement for that little movement they had.

Just wanted to share this update with the forum, in case anyone finds the results of some value.

There are a lot of things that can affect how the steering wheel is aligned, if it's only off a touch I'd just adjust it at the wheel or the steering shaft u joint. To be sure it's properly centered see how many turns it takes to get to full lock in each direction and make sure it's even.