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Discussion Starter #1
Hello All,

1991 Spider Veloce with 99,xxx miles.

I have a vibration that I am trying to eliminate.

It's a vibration that is felt and not heard.

I can start to feel it around 60kms/hr and its fairly strong at 100kms/hr (45 miles/hr and 60 miles/hour).

The vibration can be felt in the accelerator pedal and the steering wheel.

It is not RPM related. I took it up to 100km/hr, put the clutch in and took my foot off the gas pedal (rpms dropped to 1,000 or so) and no change to the vibration. It was still there.

Thinking its tire related, I had 1 shop balance all the tires and a 2nd shop verify no bent rims, out of round tires and yes, verified the tire balance.

I replaced the upper suspension arms with adjustable arms, so I also have had an alignment.

I verified that the driveshaft halves are aligned (2 arrows line up).

Not sure what to make of it.

Any help is always appreciated.

Thank you,

Vin
 

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But Mad North-Northwest
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You lose a chunk of giubo? That spins based on road speed, not engine speed. Probably want to check it for cracks or missing sections.

If not that I'd rotate the tires front to rear, see if it changes at all. That'll tell you if it's a tire problem for sure.
 

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Discussion Starter #3
You lose a chunk of giubo? That spins based on road speed, not engine speed. Probably want to check it for cracks or missing sections.

If not that I'd rotate the tires front to rear, see if it changes at all. That'll tell you if it's a tire problem for sure.
Giubo "looks" ok. No missing chunks.

Should have mentioned moving tires front to rear had no effect. Still vibrates.

Vin
 

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when did it first become noticeable
iow, was it after some work on the car?
 

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Discussion Starter #6
when did it first become noticeable
iow, was it after some work on the car?
It was noticeable as soon as I started to drive the car for the Summer season.

Over the Winter, the work I had done was:

Replace all springs
Removed Rear Axle to replace Differential friction disks
Replaced Rear Limit Straps

I Thought the vibration was caused due to the new Springs changing the alignment of the suspension and that is why I brought the car in for the wheel balance and alignment.

During the Alignment, the shop told me the Camber was way off in the front so I installed the adjustable upper arms and had the alignment complete.

Still had the vibration, so I went to the 2nd shop to verify if there were any bent rims, tire out of round and confirm the balancing was done properly. All good there.

Vin
 

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When I first bought my car a year ago I had a driveline vibration similar to what you describe. On my car the center bearing was completely worn and after removing the driveshaft I found that the two halves of the driveshaft were installed out of phase so it was not balanced. Once the bearing was reinstalled along with proper assembly and a new guibo, she runs smooth!
 

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Hi Vin,
How old is the Guibo? Did you ever change it during your ownership? Even if the Guibo looks clean and crack free from inspection on the car and not under stress, it could be very dry and has lost its flexibility characteristics, especially when under stress and when you say the vibration gets stronger as speed ramps up. This is a good indication. You will be surprised what a fresh Guibo looks and feels like on the bench compared to an old tired one.
 

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Despite two shops reporting balanced tires, if the rest of the drivetrain passes a close visual inspection, I'd go back to the tires. See if you can find a shop capable of doing a 'Road Force' balance. This simulates the weight of the car flexing the tires as they rotate. It can find things like flat spots, uneven belts, etc. Remember, you can 'balance' a square tire but it'll never drive smooth...
 

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If it was vibration free before the work, then it has to be something to do with the work....tires don't go off balance or square after one winter.

I can't see springs being the cause (drop a pan, swop a spring) nor the straps (they just hang there doing sweet nothing)

But the diff removal and the work involved there could be the problem...
did you remove the T bar to perhaps redo the big bushes?
or separate the sliding joint to regrease it and not align the splines...something like that?

(silly questions really, as I know you are very capable....:)
 

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.tires don't go off balance or square after one winter.
True. Except I once had a truck with nylon belted tires. On first driving it after being parked just overnight it'd shake the fillings out of your teeth. When parked with warm tires the nylon belts would take on the flat shape at the bottom as the cooled. It would take 20-30 minutes of driving to warm them up enough to get the belts flexible again.

Similar thing happens to my race car (MGA) on Hoosier Speedster tires. When I go out for subsequent sessions, it takes a couple of laps to warm up the tires and get them to stop vibrating. I now park and the roll the car after a few minutes so the warm treads cool off more evenly.
 

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Discussion Starter #13
I had the drive line, u-joints, center bearing, Giubo, rebuilt in May 2014. As I said, all look good visually.

I do have an unused Giubo on my shelf that I picked up somewhere along the way. Still has the metal band on it. Might be easy enough to just replace it.

I did not remove/replace the T-bar big bushings.

I did separate the sliding joint as I thought it was off by 1 spline, but that was after the vibration started. I spent a lot of time aligning those tiny little arrows and am sure they line up.

Thanks to all for their help.

Vin
 

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Discussion Starter #14
The only other work that I did just before the Winter was I replaced the rear wheel bearings and rebuilt the parking brakes.

I don't remember having the vibration after that work.

Vin
 

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Years ago I recall hearing of "shifted belts" in the tires. Could you eliminate the tires by changing one at a time?
 

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Discussion Starter #16
Years ago I recall hearing of "shifted belts" in the tires. Could you eliminate the tires by changing one at a time?
I rotated the tires, front to back, one at a time and no change.

Thank you,

Vin
 

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Vin, I don't want to scare you, but when I had a similar vibration, it turned out to be a worn "olive" on the output shaft of the gearbox. Given the cost/pain of fixing that, I hope you have a different issue.
 

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Discussion Starter #18
Vin, I don't want to scare you, but when I had a similar vibration, it turned out to be a worn "olive" on the output shaft of the gearbox. Given the cost/pain of fixing that, I hope you have a different issue.
While I can't rule out anything, when I rebuilt the transmission in 2017, both the olive and the bushing looked good.

IMG_6002.JPG


Vin
 

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That's good. I wonder if the giubo is an issue. That's a Fiat part with the ears cut off rather than a true Alfa part. I know that a lot of suppliers sell these, but my specialist doesn't think it's a good way to go.
 

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Discussion Starter #20
This is the Giubo I have on the shelf. Again, I don't remember where I got it. I don't have a receipt so it must have come from another BB member.

IMG_5489.jpg


Vin
 
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