STL 71 C3

I've rebuilt my entire front end with all new everything....(71 C3 soft top) and rear suspension as well.

Sometimes the car goes down the road and feels as good as any new car out there, steering is tight, doesn't pull and absolutely no vibration....
Then sometimes it will shake and vibrate so bad I get worried. I have checked/ re-checked everything....can't seem to figure this out.
I had it professionally aligned also.

got any ideas for me to check or look at?

Big Block Dave

Is there any common event prior to the "shakes"? Like does it do it only at a certain speed, or after making a left turn, hitting a bump etc? Any other changed parts like wheels, tires?

STL 71 C3

Good question... I'm not sure, I will try and pay more attention.

Come to think of it, always seems to be smooth after making long pull right turn. The speed doesn't make it change...

What are your thoughts if something causes it?

The wheels and tires are old... I actually am thinking about getting new tires, they are 04 from date on them.

garygnu

maybe check the rag joint on the steering shaft.jack the front up and check your ball joints and tie rod ends.do you know how much caster you have in your alignment ?

STL 71 C3

everything in front is new.

ball joints
arm bushings
wheel bearings
all new power steering cylinder and valve (with bushings)
inner and outter tie rods
rotors (shimmed within .002 runout)

starting to wonder if the tires are not the whole reason but seems like if they were, the car would shake all the time....

STL 71 C3

looked for alignment specs but can't find it....
The shop I had it done at might have a copy, I'll see if I can get it.

I don't remember there being anything wrong though, everythings seemed close to the paper I took them where I wanted it.

STL 71 C3

I wonder if anyone in the St. Louis area willing to help me with this?
I can bring to someone or maybe check it out here.

surely someone in the STL area used to build these cars can help me solve....

Blue73Shark

Besides the tires, check the wheels. I must have hit a pothole and put the wheel ever so slightly out of round, which caused the front end to shake above 45MPH. Replaced the wheel and problem solved.

Kevin68

Do a search on "cowl shake". Spreader bars have been known to help stiffen things up.

lvmyvt76

idler arm replaced?

dntoearthman

That's exactly the same problem I have or had, in the process of total front end overhaul. I did find a bad lower control arm bushing, a little play in idler arm, a week pwr steering slave cylinder, I went back w/ all moog parts and should find out soon if I have solved the dreaded shakes.I have a few post on what I have previously changed. I had my car checked by several shops w/ no real solution, if you can use somone else tires and rims is a great place to start, and a very good alighnment guy that will spend the time to do it right.

STL 71 C3

Yes, everything was replaced...with new that could be replaced...

my 76 ray

Possibly wheel balance. Rotate the front tires to the rear and if the shake moves from the steering wheel to the seat of your pants then you know the problem is in the wheels.

7dSHARK

I have a similar problem with my 70 convertible. Crazy front end shake betwen 55 and 60. The rest of the time it's perfect. Watching this post closely.

Big Block Dave

What gets me on this one is that apparently the car did not have this issue prior to the rebuilt front end...so this would probably eliminate the tires/wheels as an issue, however, I would try the above advice to switch the front and rears, just to eliminate the possibility.

For a little further info...are you feeling the vibration as a "wobble" in the steering wheel? Let us know more about the nature of the vibration itsself

AdamMeh

As you sure it's coming from the front? Are you feeling it in the steering wheel or more in the seats?

Does the steering feel change when it happens - lighter steering, heavier steering. Feeling it in the brake pedal?

I'm wondering if you're having an issue with a wheel bearing - front. If it feels stronger in the seats than the steering wheel, possible issue with the rear and it's just transferring through the car and feels like it coming from the front?

Just tossing out some things to think about when it happens.

One other note - if your tires are that old, you could have a belt separating. Can you see anything in the tires - odd bumps on the tread or sidewalls? If they are 8 going on 9 years old, they are not safe and need to be replaced either way.

Adam

Garys 68

I'm in St Louis with a 68 convertible. I can show you cowl shake on mine. Not sure how common it is on 71s.
It typically happens at around 50mph when 1 front wheel hits a bump.

Doug1

wont cost you anything either but a little time

Doug1

also try when you get it up to the speed that it shakes/vibrates, throw it into nuetral and see what happens, if instantly goes away, then you know its probably not the wheels, maybe tranny or drivetrain issue