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Discussion Starter #1
My '74 Spider project car is getting closer. I purchased it last December. All it needed was mechanical, body and interior work!

It now runs really good, but it has always had a terrible vibration that I can hear and feel. At first I thought it was coming from the driver's seat not being installed tightly, but that's not it. It is usually happening, but not always and sometimes much worse than others. It's only when the car is moving, but can be in any gear or neutral. I've looked under the car numerous times. The rubber donut thingie looks great, there are not wear marks from antyhing rubbing. There is a lot of slack in the driveline from the transmission to the rearend when the car is on jackstands and the trans is in nuetral. Is this normal? There is a very small amount of noticable play in the u-joints, should there be zero play?

Any thoughts, ideas, suggestions or comments would be greatly appreciated!
My intelligence cannot be insulted. I've read enough on this board to know how little I know.
 

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Discussion Starter #2
I'm still trying to figure out how to provide more information.

The rattle is loudest when coasting and gone when accelerating hard or stopped.

Any suggestions, thoughts, ideas, comments???
 

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Discussion Starter #4
It all looks really good underneath. All rubber looks good and everything feels nice and tight. I'm trying to make sure I am checking everything I should check before I start taking things apart and throwing money at the problem. Would u-joints be the first thing to try? Or the propshaft support and bearing?

Any suggestions at all would be greatly appreciated!
 

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Lance G said:
My '74 Spider project car is getting closer. I purchased it last December. All it needed was mechanical, body and interior work!

It now runs really good, but it has always had a terrible vibration that I can hear and feel. At first I thought it was coming from the driver's seat not being installed tightly, but that's not it. It is usually happening, but not always and sometimes much worse than others. It's only when the car is moving, but can be in any gear or neutral. I've looked under the car numerous times. The rubber donut thingie looks great, there are not wear marks from antyhing rubbing. There is a lot of slack in the driveline from the transmission to the rearend when the car is on jackstands and the trans is in nuetral. Is this normal? There is a very small amount of noticable play in the u-joints, should there be zero play?

Any thoughts, ideas, suggestions or comments would be greatly appreciated!
My intelligence cannot be insulted. I've read enough on this board to know how little I know.
Check your motor mounts! I suspect they are bad enough that your oil pan is actually sitting on the cross member and drag steering link. I KNOW because i just did the motor mounts in my 78
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Dave Andregg
 

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Discussion Starter #7
The Giubo (if that's the rubber donut thing) and the motor mounts all look great.

My problem sounds completely different from the "thump thump thump" thread that's also going on right now.

Everything is fine from standing still until I'm done going thru gears and back off the throttle. Whenever I'm not accelerating much or coasting, the noise and vibration is terrible. It doesn't matter if I'm in any gear or neutral. I've been under the car numerous times and everything looks good and I don't see any wear from anything rubbing.

Any ideas? I have no idea where to start?
 

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It's only when the car is moving, but can be in any gear or neutral.
Whenever I'm not accelerating much or coasting, the noise and vibration is terrible. It doesn't matter if I'm in any gear or neutral.
This description establishes the probblem does not occur under load. Hence, I would guess the problem relates either to the differential or the rear suspension. The first thing I would check is the bushings of the radius rods. If they are worn, they allow the rear axle to move back and forth, which would be most pronounced when you're not accelerating or braking.
 

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as it happens whilst you're coasting and is lessened when the weight is thrown forward I'd suspect the geometry.

One thing's for sure - as it's related to road speed rather than engine speed, you need to start at the rear tyres and work inwards and forwards. The problem is unlikely to be related to the front of the car as you dont feel it thru the steering wheel.

tyres ok? wheels balanced and undamaged? lugs tight? wheel bearings OK? brake disks running true? calipers binding? hubs true? wheels parallel? struts and mountings look ok? axle solid? bushes OK? diff in good nick? propshaft bearings ok? propshaft ok? gearbox idlers ok?)

Also, sounds silly, but have you checked that your wheel lugs are tight?
 

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How old are the tires? could the belts in the tires be broken? I had a 68 Mustang that sat for 5 years with 2 flat tires and that car did just what you have described here. I found it was broken belts in the tires.

If they have sat a long time they can get flat spotted. Are the tires balanced properly?

I would check the things like tires and such before looking at suspension and drive line parts.
just my 2 cents
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Dave A
 

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Discussion Starter #12
I'll start by having the tires balanced. I have 6 rims and tires and have tried different combinations, but they could all be bad.

Thanks for the suggestions, I'll keep eveyone posted.
 

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Lance G said:
How do I check the bushings of the radius rods?
Remove the bolts that hold them. If the hole through the bushing isn't round or the rubber (or plastic) has decayed, they're worn.
 

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Discussion Starter #14
Where are they and what do they look like? I have checked different parts catalogs and have not seen them mentioned or displayed in any drawings?
 

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If you don't know what a radius rod is, you should not be working on suspension parts. Don't be a danger to yourself and go to a professional instead. Join the Tennessee Chapter of AROC. More than likely, one of the members can point you to a good shop.
 

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U Joints should have zero play. No exceptions. It's the most common cause of propshaft problems.
I had one that the customer complained of "brake vibration". That was the only time it vibrated (brakes applied) It was a bad U Joint.
 

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Discussion Starter #18
Sounds like I should start with the u-joints.

Reudi, I think we might be having a language issue. I searched for the term "radius rod" on this board & found it has been used 7 times & you were 6 of them. Are you talking about the trunnion, trailing arms?
 

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Discussion Starter #19
Somehow I got into another thread called "vibration" when I thought it was this one. Very similar.

This vibration can be felt and heard. At first I felt it in my seat, now I think it is most noticable under the center hump, just behind the emergency brake handle. It happens whenever you are done accelerating, while in neutral or a gear or braking or coasting or accelerating gently.

I have now tried u-joints and tightening the motor mounts (which look new) and there is no improvement.
 
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