Fiat Dino 2400 Coupe - drivetrain vibration

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abarth4
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Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by abarth4 »

Forgot to add that if I recall correctly (it's been a long time) there were no balance weights on the shaft you have called out in yellow in your drawing. I would not expect to see any balance weights on that part of the driveline.
Charlie Bates
Metamora Illinois, USA
Fiat Dino Spider 2400 #1186
abarth4
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Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by abarth4 »

It lost my post again! I'll try again.... There were no balancing weights on the driveshaft inside the torque tube (yellow call out on your drawing) I would not expect to find balance weights there. Good luck!
Charlie Bates
Metamora Illinois, USA
Fiat Dino Spider 2400 #1186
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doublegarage
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Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by doublegarage »

Thanks Charlie - yes that's useful - that's the section that was balanced by the driveline place - but I think I'm going to take it somewhere else for triple-checking.

-Richard
Dario
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Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by Dario »

Hi, I also have a 2400 coupé, and did not have any trouble with vibrations until the day that I re-mounted the intermediate driveshaft (between the rubber coupler and the UJ) without re-aligning it to the mark I had made on the UJ. That day, I had vibrations from the drive-train at 80 kph, that disappeared at >100 kph. I undid the driveshaft, rotated it 180° and remounted it, presto, vibrations gone. That told me that the entire driveshaft (from the rubber coupler to the diff) had been balanced as one unit. Could it be the same for you?

Good luck

Dario
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doublegarage
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Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by doublegarage »

Hi Dario,

Yes that could be it - I found what I assumed were factory marks, made them larger, and have stuck with them ever since - but yes they could be rotated from where they were balanced as a system. I think you can only rotate 180 (as you did) and not 90 degrees..is that right. I will definitely try that.

Thanks,

-Richard
Dario
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Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by Dario »

Yes, it only fits at 180°steps. Definitively try turning it! You never know...

Good luck,

Dario
IA-Mike
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Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by IA-Mike »

Hey Charlie,

My '68 FIAT 124 spider which I purchased and stored until I have time to go thru it has a Torque Tube. I have been unable to find any information regarding Torque Tubes. My other FIATS have traditional drive shafts. I realize my 124 is not a DINO and not intended for this forum, but my question really relates more to the Torque Tube knowledge and since I know you have both a DINO and 124's, I hoped that it is ok to ask these questions on this forum.

1) what exactly is it and why/what is different compared to a regular drive shaft?
2) Is one better then the other?
3) are there wear items within it that need refreshing?

IA-Mike
DINO Spider bucket list future owner (hopefully)
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doublegarage
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Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by doublegarage »

Hi Mike,

The Dino is my first car with a torque-tube driveshaft - so this will be a newbie explanation - but I will do my best.

I think the problem the torque-tube tries to improve is...that the force exerted on the car's chassis when the rear axle is trying to accelerate the car is conventionally transmitted through the suspension pickup points - i.e. trailing arms, or leaf-spring attachments etc.

But with the torque-tube, that same force is transmitted by the tube - or some of it anyway. On the 2400 Dino the tube is bolted to the front of the diff - and then is mounted at the front with a large rubber ring that is clamped to the car. The rear section of the driveshaft (behind the UJ) is inside the torque tube.

So, the car accelerates, exerts a force on the wheels - the road exerts an opposing force which is now exerted on the chassis by the diff pushing forwards on the torque tube and the rubber ring at the front transmitting that force to the car.

Thus there's a device designed to connect that force to the car - instead of a more compromised absorption through conventional suspension parts,

Now, someone who's a mechanical engineer should weigh in here...

-Richard
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ThomasK
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Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by ThomasK »

I thought it may be helpful to have in adition to the drawings a photo of the driveshaft inside the torque tube. There are no balance plates on it, I also think, that this section cannot and is not made for beeing balanced.
Attachments
Driveshaft.jpg
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doublegarage
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Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by doublegarage »

Thanks Thomas.

Yes that's the part, and the more I think about it, the crazier it seems that there is a balance weight welded on. If I remember it looked like a normal curved balancing "washer" that you would see welded to the outside of a tubular driveshaft - but not welded to a small shaft like this.

So I think I'll try the following:
1) reverse the coupling that's in front of this section (i.e. rotate two driveshaft halves 180degrees from where it is today - if that doesn't work...
2) dismantle (again) this part of the drive shaft and remove this added weight. then...
3) really don't know - I will be clean out of ideas.

thanks again for help everyone

-Richard
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