creak / graunch noise from rear suspension

[Otter74]

Having just gotten back this morning from a ~1600 mile trip to Atlanta and back, I am more aware than ever of a noise from my car's right rear suspension. I hear it on compression in the right rear wheel, at low speed - maybe high-road-speed inputs cause it, but if so you can't hear it. I will hear it, e.g., when letting the clutch out from a stop, or when backing out of a driveway over an apron.

I would describe it is a momentary creaking/graunching type of noise. it seems to be getting transmitted through the body shell, as I can hear it quite clearly from the right rear passenger compartment. The suspension has monoballs and polybropnze bushings. I lube those at every oil change and it doesn't sound like a dry bushing anyway. It plausibly sounds like a slightly loose shock mount (not a very loose one that would casue a clunk) but, while I haven't had time to force-check tightness, there's no visual evidence of anything off. This would only seem to leave the torsion bar as a candidate. What, then, should I be looking for as evidence, and if it is the torsion bar, what is actually happening? I'd suppose the bar is rubbing on the tube it's housed in, but how? trailing arm bearing *looks* good.

Edit: I should also add that I have a slightly worn U-joint in my steering column that I will be replacing soon, which tracks with a very slightly off feel in turn-in response of the body. I am aware that a rear suspension issue is just as likely to cause assymetrical turn-in behavior as a front suspension or steering issue.

[RDM]

Otter,

I had a similar problem, though that might not help you as I've still got rubber suspension parts and that's where the problem was. The spring plate bushing is supposed to stay glued to the spring plate, and when it stops being glued to the spring plate, it makes a granching noise over speed bumps and the like at low speed.

Here's my thread: Rear suspension "granch"

[Otter74]

Thanks, RDM.

It did occur to me after writing that I could have a cracked anti-roll bar mount. However, they were fine the last time I inspected them in the fall and I quick look with a headlamp the other evening didn't show anything obviously wrong.

I'll be able to explore it when I put the car up for an oil change and valve adjustment soon.

[Kemo]

I had some creaking sounds in the back and it turned out to be some loose bolts on the motor cross-mount. I cant believe I left those un-torqued but I caught it before any problems. so any loose bolt back there could be a problem, or even a motor mount bolt I would guess. rev the motor by hand and see if you have excessive motor movement left-to-right.

[Otter74]

Bringing this back from 2018...this noise seems to have gotten gradually worse, and hwas quite evident when I drove it this weekend. I would hear it when, say, backing out of the garage over the apron; I can also hear it just after I come to a stop at a light.

When I parked at my destination, I was able to reproduce it while parked by pushing on the left rear bumper with my foot (it's definitely coming from the left side). The noise would occur, or continue, *after* the car had settled. With my hand on the tire when I pushed down, I could feel the noise being transmitted through the wheel. It sounded like it was coming from the spring plate bushing, not the hub. Eventually I was able to put my hand on the spring plate bushing cover and could feel it in my hand there.

My car is an '80 SC with monoballs in the semi-trailing arms and Elephant polybronze bushings at the spring plates/torsion bars (also in the front). These were installed I think about 20k miles ago by the PO. I grease everything in the suspension with each oil change, every 5k miles.

It's due for an oil change and valve adjustment so it'll be up on stands imminently. I'll check wheel bearing tightness but that seems unlikely since I can hear it at the spring plate cover.

I may try disconnecting the sway bar but that seems unlikely as the mounts look OK.

Is there any way for me to validate the condition of the bushing without pulling stuff beyonf the torsion bar cover off? Other than greasing it again and looking for a change of behavior.

Anything I'm missing?

[RDM]

Originally Posted by Kemo

I had some creaking sounds in the back and it turned out to be some loose bolts on the motor cross-mount. I cant believe I left those un-torqued but I caught it before any problems. so any loose bolt back there could be a problem, or even a motor mount bolt I would guess. rev the motor by hand and see if you have excessive motor movement left-to-right.

Interesting. When I changed my muffler I found this:



Note there's only one bolt there of the six that attach to the pully well at the back of the engine, and it's not exactly tight!



I fished these out of the pully well.

I shudder to think of what almost happened. I recommend you check this.

[fizeus]

I had your exact same problem... It has gone away replacing rear inner suspension bushings....

If you want to check take some speed on a desert road... Put in neutral and switch off the engine... If the problem is synced with road asperities.
You can try to use some silicon grease but it will come back after a while.
Do not lube with engine oil... Bushings require silicon or lithium grease

[Flojo]

Had the same once... old and hardened sway bar bushings at rear.
At first, I lubed them a little wd40... noise gone.
Eventually I changed them.
Still no more noise.