!970 Convertible, 4 speed, SBC350

This is my wife's car, so I don't have much first hand experience with the symptoms, but she told me she was driving it on the freeway and at about 50mph, the car started to really shake. She downplays any problem with the car, so I think the shaking was significant. She got off the freeway (so slowed down the car), and the shaking went away. I need to figure out why that's happening, which may be directly related to this post or not at all!.
Problem 1:
I initially thought maybe a loose wheel or something like that because I replaced front brakes a few months ago. (she only drives the car once in a while). The lug nuts were tight, so I jacked the car up and if I stand on the side of the car and grab the top of the tire and pull toward me, there is a little movement. I get the same movement on both the passenger and driver side front wheels. I do not get any movement when I do the same test on the back wheels. Is this movement normal? I feels like maybe 1/8" movement. Wondering if it's normal because its the same on both sides or if this needs to be fixed.
Problem 2
I jacked up the back of the car to do the same pull test on the wheel and noticed 3 things:
1. Rear leaf spring looks a little rusted and coming apart. Do I need to replace it? (picture below)
2. Rear left side shock-absorber top was not connected to the car. The bolt was completely gone, so need to replace it. Don't know if that has something to do with shaking or not.
3. Inside of rear right tire was damaged. Tires are very old and need to be replaced, but wanted to include this info

So I guess the main question are:
Should I replace the Leaf Spring? (thinking yes, but wanted to ask the group)
is the ~1/8" side to side play in the front wheels normal?
Any ideas on the shaking? I want to fix the shock,, tires, and spring (if needed) before doing any additional road test.


Thanks in advance

 

Your wife found some harmonic resonance at 50 mph.

The appearance of the leaf spring doesn't matter for function, but many of us are happier with low-arch composite springs from Van Steel, so that's my suggestion if you do replace it. The spring should have nothing do to with your symptoms, though.

I'd change the tires first. Just an imbalanced tire, combined with some worn bushings, could be most of the problem. Check the rear trailing arm and strut rod bushings, too. And fix the shock bushing. Those look like new Bilsteins. I wonder what happened.

Can you post a photo of the tire damage? Would a new tire suffer the same damage? Is it rubbing on the parking brake cable, for example?

You may need a front suspension rebuilt, too. Is the play in the hub bearings, or elsewhere?

 

Yep, agree, the rear spring looks fine. The leaves are all independent and the "separation" in the top two or three is normal.

If the tires are old (8-10+ years), change them ASAP. We have seen pics of tires that came apart and damaged fenders or worse – it's not pretty. Yours could have lost a weight or could be flat-spotted, causing vibration at speed. A disintegrating tire puts your wife's life, and the lives of those around her, in serious danger.
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A little guidance on checking for worn suspension:
Your front wheel movement when rocking the tires from 12:00 to 6:00 is focusing more on the wheel bearing play. 1/8" sounds like a bit much. Do you have the Chevrolet Chassis Service manual for your '70? It has the procedure for setting the bearings if they have adequate grease and are not at the end of their lives.

Big movement between 12 and 6 with clunking indicates worn ball joints.

Rock each front tire between 9:00 and 3:00. You shouldn't have much or any play in this direction. Play here indicates worn steering tie-rods.

None of these replacement parts are special to Corvettes, but there are quality differences between brands, so ask here if you are going to do this sort of work to the car.
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Now go get new tires on there!

 

Glad to hear the leaf spring is fine. I took a closer look at the tire that had damage, and it is completely warped, I don't know how it didn't burst, but I'm thankful it didn't. Tires are already on order!
The play in the front tires does seem to be at 12 and 6, not 9 and 3, and isn't ~1/8", more like ~1/16", so will add the ball joints to the project list.
Now for mounting the upper rear shock:
I looked up the part number for the upper rear shock mounting bolt, and it is 5-grade 7/16 20, 2-1/8" long, and only has the last 1/2" threaded. I can order it, but will take 2 weeks to get. Has anyone used a 2-1/2" bolt or a 2" bolt that is more than the 1/2" threading? Is this a problem?? If it is, maybe I can use the 2" or 2-1/2" bolt then change it our in a few weeks with the 2-1/8 bolt w/ 1/2" threading comes in

 

Fantastic tire news!

Before even considering ball joints, I'd look at the front hub bearings. In my experience, worn out ball joints aren't usually that subtle and you'll be well-served to inspect and adjust the bearings anyway if you do need ball joints. With the front raised on jack stands but tire still mounted, remove the wheel bearing cap - it's just pressed in and you can usually work it off with gentle prying and pulling. Resist using large channel-locks that can crush the cap. Behind the cap you should see a cotter pin, large nut, and large washer -- it should all be pretty well slathered in gooey grease. If the grease is hardened to any degree, I'd recommend a full bearing removal, spindle cleaning, and regrease.

In a very general overview, to set the bearing pre-load, with the cotter pin removed, you basically tighten the nut until the wheel rotation begins to be affected. Then back off to the nearest slot in the nut that will allow a new cotter pin to be inserted. I'll see if I can post the Chev. Service Manual pages that details it.

 

CJB,

That happened to me yrs ago.

Check your PS reservoir. Your PS Control Valve either ran low of fluid, or something blocked one of the pressure lines. Or the C.V. is shot.
Then the C.V. favors right turns, then favors left turns at an alarming rate. The CV sends an alternating rapid pressure signals to the hyd ram cyl.
Shakes violently, almost like a shimmy until it balances out.

With mine, it was several minutes after replacing PS hose. Evidently still had air in the system.

Has work been done on your PS system lately?

 

Let me back up a bit: with the front on jack stands with tires mounted, you should be able to see slop in the ball joints by rocking the wheels between 12 and 6. You need to be able to forcefully rock the wheel and view the upper then lower ball joints - not something very easily done on jack stands by yourself. Maybe set up your phone and video the joints as you rock the wheel.

Here are the Chev. instructions for wheel bearings:

 

OP mentions anchor bolt gone not so much bushing missing. Yikes. Having one side of the car undamped seems like it might cause some driving
issues. I think I'd start there with the lowest cost/shortest time frame fix and redrive.

 

Yup!

For my Bilsteins, I had to do some custom fitting, as the stock bolts left some slack. Perhaps I needed a sleeve? Be sure to use nylocks to prevent the bolt from magically disappearing again.

 

This is your problem. Your wife was absolutely correct in reducing speed. As tires wear, balance is off. If that wheel is not dampened, speed (wheel RPM) magnifies the out-of-balance condition causing the wheel assembly and suspension to wildly move up and down. My wife and I were traveling on an interstate not far from California when a small pick-up with a camper shell filled with household items passed us approaching a 3% incline. The rear wheel was bouncing up and down, at times getting 3-4 inches off the road. On the downgrade about 2 miles down the road, the pick-up was in the median having flipped several times scattering truck parts and household items for several hundred feet. A lot of drivers had already stopped and a State car was coming. I do not know the condition of the occupants.