kellsdad

I love it when someone other than me works "resonant frequency" into the conversation.

DansYellow66

Could also be the old worn transmission tail shaft bushing and yoke thing. I’ve always suggested crawling under the car and grasping the yoke or knuckle of the driveshaft and try to move it from side to side to check for movement in the bushing. Well, that recently failed to work for me on my 66 4-speed Satellite. Wiggling it side to side seemed to show just a bit of movement. Then I tried it up and down and that was a whole lot different - lots of movement. And that can create a vibration that may happen at different speeds depending on things like the u- joints, driveshaft balance, straightness, trans mount, etc, in the same manner as Jim described in #17 above for shocks and tires. It’s all just guess work working off second hand observations.

dplotkin

I can confirm. In 9 cars and 21 years balancing a driveshaft has never paid off (for me). Every and there have been many instance of vibration in my motor pool was tires or suspension sometimes both. That new parts are present is meaningless today. Get under the car and look for play in the front end where there should be none. The guy who balanced the tires should have seen any gross imbalance. But Coker can be hit or miss.

Dan

68sixspeed

Interesting, I’m chasing the same thing on a 67 at approx 55mph. it has a rebuilt front end (rear too), recent shocks,, new bfg red stripe tires (are those Coker?). I’m going to check the balance on the tires tomorrow but the previous owner says the car has always done it. No real crazy shake in the steering wheel but the front end gets bouncy and you can see the hood shutter.

SWCDuke

The natural frequency of the base C2 front suspension is about 12.5 Hz, which corresponds to a road speed of about 60 MPH, assuming tires with close to OE revs/mile. Out of balance and out of round cause the same vibration in the vicinity of the suspension natural frequency. A tire may be perfectly balanced, but if the wheel/tire assembly is more than about 30 thou out of round, it's going to feel like an unbalance. The out of round could be the tire, wheel, or some combination of both.

Do a Web search and find a local shop with a Hunter GSP 9700. It will detect an out of round condition. It may be possible to minimize it by rotating the tire on the wheel, or shaving the tire. Or the tire and or wheel may be so far out that one or both need to be replaced.

You should certainly do the above before condemning the driveshaft.

Duke

68sixspeed

Duke- thanks, I'll give that a shot. If not, would the wheels/tires from my 63 fit the 67 ok? (that car doesn't have any issue) I wasn't sure if there was a backspace difference from the older drum brake cars to a 67/disc brake? thx Dan

Railroadman

The original steel wheels from drum brakes in early C-2's won't clear the disc brakes on newer years.

Viet Nam Vett

Well that is refreshing.. Some else other then me knows about the HUNTER ROAD FORCE Balancer. My tires on both my 65 Ratwagon and My HUMMER H2 are road force balanced. What a diff it makes. I like how the Hunter finds the heavy spot of the wheel.. and the tire and shows where to rotate them apposed to each other. Not to mention the Roller that applies down force.

After the balancing the ride is fantastic. I've had the Vette up to 130 MPH..( Never Again) doing the Kerbeck Corvette Toys for Tot's Run on the AC Expressway. Not one shake anywhere. What scared me was I got Power steering and 130 and some front end lift.... And I don't have PS..

If you haven't tried the Hunter road force balancer.... Try it next time...and treat yourself to a safe and smooth ride.

vegasthomas

How many miles on the car? How about half-shaft u-joints?

sbsurfer

If you have ruled out the wheel/tire balance I would look into driveshaft balance, half shaft balance and the driveshaft angle as well.

I had a similar issue on my 67 Camaro with a C4 rear end and it ended up being the driveshaft angle being off just a bit.

68sixspeed

thanks, I have the original steel wheels/hubcaps in the loft, but the radials for the 63 are on a set of bolt on knockoff style rims, so those should clear I hope. thanks for the ideas, I'll try the wheels and if that doesn't work go for the driveshaft next. It seems similar to the OP's problem so I figure I'd tag onto the thread, didn't mean to take it over! Similar also that the suspension components and shocks front and rear are new or under a thousand miles on them.

If the 63 wheel/tire swap fixes it I'll try to find the road force balancer on the 67 wheels/tires, I checked a few local shops and so far no luck but someone must have one near me.

-Dan

Chief Dan

Latest news: This is getting to be a real PITA! About a month ago I took the car (64 convertible) to a different shop from the one who installed the new Cooper whitewalls. I wanted them to re-check the balance of the tires because I had this 55mph shake. They checked the car over and said front end seemed tight, wheel bearings were good but they found a bent rim. Fine, ordered a new rim and had them mount and balance it. No difference in the shake. A week or so ago I noticed that the front tires were wearing on the insides, so I set up an appointment to have the front end aligned. Dropped the car off yesterday morning and just after I got home, they called and said I should come and see the problems they found. Young guy doing the alignment ( Not the one who said wheel bearings were good) said he couldn't align it because the rear wheel bearings and rear trailing arm bushings were bad. I was told that he could order the parts and do the job and I said that I would also look into getting the parts. Then I was told that the labor was $95 per hour if the shop bought the parts but $125 per hour if I sourced the parts.
Got home and did some research here and found what a job this is, and the special tools required. Also, the mechanic shook the tire from 12-6 and found the play. One of our learned members has stated in a previous post that this play could be coming from the rear axle itself. I have called the shop and told them to hold off on ordering parts. Now I don't know who to believe so I think my next trick is just have another shop align the front to save my front tires and search for someone qualified to tell me if the axle bearings are good or not and go from there.
Another question. When I first got the car last summer we put it up on the lift to flush the brake system and noticed that one of the outboard half shaft u-joints had a bolt missing and one very loose. We put in a grade 8 hardware store bolt and I think it was a little longer than the stock bolts. Just wondering if the longer bolt would cause an unbalanced situation? Thanks for listing guys, sorry for the long rant.

Viet Nam Vett

Well Chief,
Sorry to hear about the run around and the confusion. I know when I first got my Ratwagon I had the Rear Trailing Arms rebuilt by Bairs http://www.bairscorvette.com/services/index.html
They did my Rear Diff and the trailing arms. They even send you the special box to UPS them back. The Members here have given some good advice as far as troubleshooting. My thoughts were when I first drove my 65 was that there was something not right with the drive ability of my Vette. I had some wondering and some vibration. which lead me to just get the chassis done. Hence the rebuild .

I also did Ball Joints and Wheel bearings and tires. And of course had the tires balanced and checked. Also did New Break Calibers ...Not rebuilds. Anyway .. Maybe it's time just to pull the trigger and do it all. If Not ..... I'm sure the experts here will try and help out with your problem.

Good Luck with your quest.

dplotkin

I've read all your posts on this thread. The 63-67 Corvette has a complicated chassis with a lot of wearable parts any one or more of which will cause vibrations, pulls, wobbles and noises. It makes no sense to try to zero in on the cause when known problems exist. Before I kept searching and trying new things rebuild those trailing arms and replace any and all bushings front and rear, including ball joints if they are anything but spec tight. Once everything is tight, have a 4 wheel alignment done by a shop that routinely does C2 Corvettes or at least other complicated vintage IRS cars. You may still have some vibration after that, but it will then be easier to find and the car will perform eminently better.

The chassis on my L78 is new and it drives like I imagine it did when new. Yours will too. But there will be some pain involved. There must be pain if there is to be a gain.

Dan

Viet Nam Vett

Makes Sense ...Just a Little $ Pain..​​​​​​​

CaptainEgg

you have a pm

mashinter

Does your car have the steering shock (stabilizer)?

Chief Dan

The car has power steering, I'm not sure about a stabilizer

jim lockwood

The two are mutually exclusive.

truenorthfree

Have you solved your shake problem?
I had the same issue and it came down to the bushings at all 4 corners of the vehicle.
Took the old ones out and they had the consistency of marshmallows and where easily squeezed by my fingers.
Put in all new ones and the car rides like a dream now.