Scary noise from rear suspension

[Jeffrey S.]

We took a ride this evening in our '69 for ice cream and on the way home I heard a very serious sounding noise coming from the left rear wheel when I made a right turn under light acceleration. No noise on turning left, going straight or turning while braking or coasting. Nothing looked broken, scraped, etc. but I noticed that the leaves of the rear spring were not stacked straight and the liners are also off. Could it be the leaves of the spring scraping while moving in a turn? Any thoughts? I will get the car off the ground remove the rear wheels this weekend and have a look but I have a feeling that it is something serious (and expensive). Thanks for you help.
Jeff

[Patrick H.]

Re: Scary noise from rear suspension

I'd check the spring as you mentioned.

Other item that comes to mind is rear bearing - have you checked them lately?

[Joe L.]

Re: Scary noise from rear suspension

We took a ride this evening in our '69 for ice cream and on the way home I heard a very serious sounding noise coming from the left rear wheel when I made a right turn under light acceleration. No noise on turning left, going straight or turning while braking or coasting. Nothing looked broken, scraped, etc. but I noticed that the leaves of the rear spring were not stacked straight and the liners are also off. Could it be the leaves of the spring scraping while moving in a turn? Any thoughts? I will get the car off the ground remove the rear wheels this weekend and have a look but I have a feeling that it is something serious (and expensive). Thanks for you help.
Jeff

Jeff------


I agree with Patrick. Since you've apparently noticed some sort of anomaly with the spring, it's the first thing to check. You might have a broken leaf (some leaf other than the bottom leaf because if that one breaks you'll know about it IMMEDIATELY). Also check the 4 spring plate retainer bolts for being present and properly torqued (torque these only with the spring de-arched in the normalized suspension configuration).

Other possibilities are the rear wheel bearings as Patrick mentioned, the half-shaft u-joints, or some internal problem with the differential.

[Jeffrey S.]

Re: Scary noise from rear suspension

Patrick & Joe:
Thanks for the responses. The rear wheel bearings were replaced I would say well short of 10,000 miles ago but they have not been checked since. I will check the spring when I can get the car off the ground this weekend. All 4 bolts are there and I will check torque as well. The u-joints are not new but not the original ones. How can these be checked? Do I try to rotate the half shaft by hand to check for play? The noise seems to be coming right from the wheel area so I kind of doubt that it is the differential. I know from experience what you said about a broken main leaf- been there, done that many years ago. Thanks again for your help.
Jeff

[Wayne W.]

Re: Scary noise from rear suspension

Posi clutches. Change the fluid and additive.

[Patrick H.]

Re: Scary noise from rear suspension

Posi clutches. Change the fluid and additive.

That was my next thought too, though I know that Jeff normally keeps his car exceptionally well maintained and it's probably been done recently.

[Joe L.]

Re: Scary noise from rear suspension

Patrick & Joe:
Thanks for the responses. The rear wheel bearings were replaced I would say well short of 10,000 miles ago but they have not been checked since. I will check the spring when I can get the car off the ground this weekend. All 4 bolts are there and I will check torque as well. The u-joints are not new but not the original ones. How can these be checked? Do I try to rotate the half shaft by hand to check for play? The noise seems to be coming right from the wheel area so I kind of doubt that it is the differential. I know from experience what you said about a broken main leaf- been there, done that many years ago. Thanks again for your help.
Jeff

Jeff------


My experience has been that unless the u-joints are WAY, WAY gone, you'll not be able to detect problems without removing them from the car and inspecting. I've even seen situations when the half shafts were removed from the car and the u-joint caps removed, the bearings were "poured out" as powdered rust, yet the problem could not be discerned with the half shafts on the car.

[Jeffrey S.]

Re: Scary noise from rear suspension

Wayne:
Thanks for the input but this noise is way different than the posi clutch "chatter" That's more like a thumping noise that is present on turning in either direction whether under acceleration or not and most often when turning more slowly. This is more a metal on metal grinding, screeching sound and it almost feels like the tires are spinning. I'm leaning toward wheel bearings or u-joint failure and I'm really hoping for the latter or maybe, as was suggested, a broken spring leaf.
Jeff

[Joe L.]

Re: Scary noise from rear suspension

Wayne:
Thanks for the input but this noise is way different than the posi clutch "chatter" That's more like a thumping noise that is present on turning in either direction whether under acceleration or not and most often when turning more slowly. This is more a metal on metal grinding, screeching sound and it almost feels like the tires are spinning. I'm leaning toward wheel bearings or u-joint failure and I'm really hoping for the latter or maybe, as was suggested, a broken spring leaf.
Jeff

Jeff-------


Just to be clear, I'm not suggesting that the noise you describe sounds like it could be a broken spring leaf. I'm just saying that since you apparently noted some anomaly with the spring, that would be a good thing to check out FIRST, especially since checking that out is really not too difficult.

Based upon what I can tell from your description of the sound, it sounds more like u-joints to me.

If you get to the point of removing the u-joints, remember that any u-joint which evidences ANY brinneling on ANY of the four trunions is SCRAP. However, if the u-joints are bad enough to cause noise, the chances are they'll be no doubt about them when you look at the bearings and/or trunnions.

[Terry M.]

Re: Scary noise from rear suspension

We took a ride this evening in our '69 for ice cream and on the way home I heard a very serious sounding noise coming from the left rear wheel when I made a right turn under light acceleration. No noise on turning left, going straight or turning while braking or coasting. Nothing looked broken, scraped, etc. but I noticed that the leaves of the rear spring were not stacked straight and the liners are also off. Could it be the leaves of the spring scraping while moving in a turn? Any thoughts? I will get the car off the ground remove the rear wheels this weekend and have a look but I have a feeling that it is something serious (and expensive). Thanks for you help.
Jeff

Don't ignore the possibility that some parts of the parking brake have come apart. If the rear rotors are not riveted on, this is a relatively (compared to universal joints) easy inspection. Of course if the rotors are riveted THAT is a whole other story.

[Jeffrey S.]

Re: Scary noise from rear suspension

Joe-
I understand exactly what you meant and I thank you for the follow up. I am also thinking more and more that it's a u-joint. If a bearing is failing, the noise would be there no matter which direction the car is going and at all speeds. U-joints are "stress" sensitive. Next time I get to the car and I put it in gear (automatic) I will listen very carefully for any clunks that would also indicate u-joints.
Terry-
Funny you should mention that! I spoke earlier this afternoon to the Corvette mechanic I use when I can't fix something and he mentioned the same thing. I have all stainless hardware in there but a spring could have broken, etc. so I will check that also.
Jeff

[Michael G.]

Re: Scary noise from rear suspension

Jeff, You mentioned the leafs not stacked straight and liners a little ascew. Is it possible that there is some movement of the pumpkin taking place? I know it's a long shot but this could allow the leaves to shift position. Good luck.

[David S.]

Re: Scary noise from rear suspension

Check to make sure the bolt that holds the spring together did not break. I have taken several springs apart and had to replace the center bolt because the threads weaken and the nut does not hold the pressure.

-Dave

[Jeffrey S.]

Re: Scary noise from rear suspension

I finally had a chance to get the left rear tire off the floor to check things out. First I grabbed the tire at each side and checked for wheel bearing play and it seemed tight. I grabbed the top and bottom and did the same. The bearing seemed like it was tight but it felt like the whole assembly was moving a bit. I got underneath and I couldn't believe what I found. The four bolts that hold the strut rod bracket to the differential were GONE! Not just 1 or 2 but all four. Nothing was holding the strut rods in place. When I drove the car the last time I did feel like the rear end was a little squirmy and when I parked it I noticed the right rear was somewhat toed out but I figured it was just time for an adjustment. So now I need to determine:
1. Did they just vibrate out?
2. Did they strip out of the cast iron (helicoil to fix)?
3. Did they break off? I could see into at least one hole and it was empty.
4. Did the cast iron break away (please let it be 1-3).
5. What was damaged in the trailing arm, etc.? Any thoughts on what could have been damaged?
I did not have the time to take the bracket down to check this out but next time I will get the right rear off the ground and and move the assembly back to the middle and see.
I suspect that the noise I heard was something scraping the trailing arm when the assembly was forced to one side in the turn- it looked like 1 french lock was almost touching it at rest.
I will need to buy 4 replacement bolts so if anyone can tell me what the correct headmarking was for these I would appreciate it.
Jeff

[Joe L.]

Re: Scary noise from rear suspension

I finally had a chance to get the left rear tire off the floor to check things out. First I grabbed the tire at each side and checked for wheel bearing play and it seemed tight. I grabbed the top and bottom and did the same. The bearing seemed like it was tight but it felt like the whole assembly was moving a bit. I got underneath and I couldn't believe what I found. The four bolts that hold the strut rod bracket to the differential were GONE! Not just 1 or 2 but all four. Nothing was holding the strut rods in place. When I drove the car the last time I did feel like the rear end was a little squirmy and when I parked it I noticed the right rear was somewhat toed out but I figured it was just time for an adjustment. So now I need to determine:
1. Did they just vibrate out?
2. Did they strip out of the cast iron (helicoil to fix)?
3. Did they break off? I could see into at least one hole and it was empty.
4. Did the cast iron break away (please let it be 1-3).
5. What was damaged in the trailing arm, etc.? Any thoughts on what could have been damaged?
I did not have the time to take the bracket down to check this out but next time I will get the right rear off the ground and and move the assembly back to the middle and see.
I suspect that the noise I heard was something scraping the trailing arm when the assembly was forced to one side in the turn- it looked like 1 french lock was almost touching it at rest.
I will need to buy 4 replacement bolts so if anyone can tell me what the correct headmarking was for these I would appreciate it.
Jeff

Jeff------


I've never heard of this occurring but I don't think you have a major problem here. I suspect that the bolts just loosened and fell out because they were not torqued properly and they were likely not even tightened, at all. It might be that some previous servicer installed the bolts finger tight and forgot to finish tighten and torque them. I doubt that the bolts broke off or that they stripped out. I REALLY doubt that the cast iron broke away. However, the only way to find out is to carefully inspect them. I think that, at most, what you might have to do is Heli-Coil one or more of the tappings. This is easy.

The bolts, GM #454905, were standard hex head, trimmed, 3/8-16 X 7/8", and GM 300M material grade (SAE grade 8). "WB" and "A" were among the headmarkings but I doubt they were the only ones used.