Fiat Dino 2400 Coupe - drivetrain vibration

Technical Topics and Discussions

Moderator: alh

User avatar
ThomasK
Posts: 187
Joined: Mon Dec 30, 2013 12:44 pm
Dino: Fiat Dino 2.4 Coupe

Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by ThomasK »

If that doesn´t work, maybe I can sell you one of my spare inner shafts if you need one.
KR Thomas
User avatar
doublegarage
Posts: 212
Joined: Thu Nov 14, 2013 4:22 am
Dino: Fiat Dino 2.4 Coupe
Location: California, USA

Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by doublegarage »

Today, as suggested earlier by Dario, I flipped the orientation of the coupling at the rear of the driveshaft.

This is right behind the UJ, just before the shaft goes into the torque-tube. As Dario says, you can undo the 4 bolts, rotate it 180degrees (n0t 90) and replace. I had found some sort of factory mark the first time that I disassembled it - so I've stuck with those ever since - but this was definitely worth a try - I don't know why I didn't try it earlier.

So...it made a big improvement - thanks Dario! The car definitely is now much smoother when you lift of the gas and coast - that was when it was worst, but now that seems way better.

If anything it now vibrates more noticeably under load - accelerating up hills etc. But that could just now be "the next biggest vibration" that I'm no noticing because the coasting vibration is so much better now.

Next step might be to remove the crazy balance weight that's on the thin section inside the torque-tube. Bit I think I'll drive it a while before I attempt that.

Thanks everyone for the help.

-Richard
User avatar
doublegarage
Posts: 212
Joined: Thu Nov 14, 2013 4:22 am
Dino: Fiat Dino 2.4 Coupe
Location: California, USA

Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by doublegarage »

After a longer drive (~45 minutes) this morning it's working better still. Strange this, that it always gets better when the car warms up. That seems to suggest a rubber component that works better when it's softer.

candidates:
engine mounts: probably the first rubber thing to heat up - but they're brand new and the same thing happened before I replaced them
driveshaft doughnut: at the rear of the gear box, therefore would warm up slowly I suppose (it's new too)
torque tube "nose mount": would also be very slow to warm up, if at all, but definitely in the right place to affect vibrations (also new)

then after that it's bushings in the rear suspension (most are new) and shock absorbers (old). I guess I should do the rear shocks but crazily over priced for now.

-Richard
User avatar
doublegarage
Posts: 212
Joined: Thu Nov 14, 2013 4:22 am
Dino: Fiat Dino 2.4 Coupe
Location: California, USA

Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by doublegarage »

I drove home via the "scenic route" this evening and had more time to experiment. The worst vibration is at 70km/h while coasting (foot off throttle) downhill or on the flat. It's better than it used to be, but this still just isn't right.

It feels like a loud "hum" - like from an old radio :-)

Calculating 70km/h = 9.6 revolutions/second (rps) of the rear wheels.
The differential ratio is 8/39 - therefore the driveshaft rotational speed would be about 47 rps
which gives about 47Hz - just like an old radio (in Europe anyway)

so I had been wondering whether this could be from the rear axle, but it seems like despite balancing the driveshaft - it still vibrates. So I think I need to get rid of this stupid weight welded to the side of the shaft inside the torque tube. sigh.
Georg
Posts: 198
Joined: Thu Jan 02, 2014 6:55 pm
Dino: Fiat Dino 2.4 Spider
Location: Germany

Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by Georg »

Hi Richard

I have experienced this problem several years ago with my FIAT Dino 2400 Coupé and after a long search the solution was found in several details at the propeller shaft.

At the inner side of the propeller’s casted front end (where the hardy disk is Catalogue B3.01) is a steel bush which embraces / connects with a spherically formed ring on the primary gearbox shaft’s end (Fiat part no. 421 7547 on page B2.04 of the parts catalogue). This ring centres the propeller shaft with the gearbox’ primary shaft. An often neglected maintenance detail is regularly greasing / lubricating the propeller shaft’s front. There is a small greasing nipple. If you do not grease here over time the bush and the sliding front end of the shaft run dry and wear out. Remove the propeller shaft from the car and feel with your fingertip if the surface of the bush is still straight or already eroded. A millimetre of erosion leads to a propeller shaft that turns out of the centre and causes vibrations. Push, pull and twist the front end on the main body of the propeller shaft. Again, no grease here causes wear of the shaft’s indenting. My car had these vibrations at km/h 80-90. If to be replaced the bush must be reproduced on a turning centre as you will probably not find it as an individual spare part. It must be hardened. If the denting has tolerance it is hard to repair. Years back when I was engaged with this problem I was happy to find a spare part at GKN, and they also welded the part on the shaft. Perhaps you consult with GKN?

It is indispensible that you have the complete propeller shaft rebalanced in one peace. The specialist doing this work must have a machine that can balance on 3 “levels”. Only balancing the main propeller shaft 4639525 without being connected to the smaller shaft 4201181 (catalogue page B3.16) is useless and wasted money. Make sure that the ball bearing 28042330 in the rear tube is good.

The front end of the propeller shaft is connected to the gear box with the hardy disk. Make sure that all 8 screws and nuts are the same. Different size and length leads to a few grams difference and can cause vibrations.

All this helped to eliminate the vibrations at my Dino.

Good luck.

Georg
Georg
Posts: 198
Joined: Thu Jan 02, 2014 6:55 pm
Dino: Fiat Dino 2.4 Spider
Location: Germany

Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by Georg »

Fotos of bush and spherical ring, indenting and casted shaft's front end and position of bush in casted front end
Attachments
IMG_6856.JPG
IMG_6855.JPG
IMG_6849.JPG
User avatar
doublegarage
Posts: 212
Joined: Thu Nov 14, 2013 4:22 am
Dino: Fiat Dino 2.4 Coupe
Location: California, USA

Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by doublegarage »

Hello Georg.

Thanks for your reply - that's very interesting information. I should have thought about this area earlier, because Alfa Romeos have the exact same problem. A spherical centering "olive" on the end of gthe gearbox output shaft, and a small circular bush in the nose of the propshaft. It's quite easy to replace the one in the propshaft - and requires a full gearbox rebuild to replace the olive.

On my Dino I never felt inside the nose of the propshaft as you suggest - I should have!. I just filled it with grease and pushed it back on. So I will look at that as soon as possible and replace somehow if it's loose. I really hope the olive is good...

The push/pull part you mention (splined area I think you're referring to) is in good shape as far as I could tell.

Balancing as a whole - yes I certainly didn't do that - only the main external black section. The piece inside the torque-tube seemed like it was so well constrained between two bearings (and is short) that it couldn't produce this high amplitude vibration - but - you're right,I must try to find someone who can do it as a whole. Our local brilliant propshaft balancer passed away last year, and so all that's left are the pickup truck guys...I will have to find someone to send it to.

The screws in the hardy disk (great name! that's a new one :-) - I have heard flex-disk, giubo, guibo, donut, doughnut etc etc) are all brand new and so hopefully balanced properly.

Thanks again for these great ideas!! This is why forums like this exist - how did we ever own these cars before the internet? People are sending me photos of disassembled propshafts with worn out pieces etc.

-Richard
User avatar
doublegarage
Posts: 212
Joined: Thu Nov 14, 2013 4:22 am
Dino: Fiat Dino 2.4 Coupe
Location: California, USA

Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by doublegarage »

Does anyone have a spare propshaft (driveshaft)? Especially the front "nose" section photographed by Georg above.

Speaking with Colin at Superformance he is interested in sourcing the correct replacement bushing for this problem. But, as with most issues like this, he needs to see an actual sample before he can source them.

I'm willing to lend him mine and have the car out of action for a while - but just wondering whether anyone has one in a box somewhere that they could lend him? (Has to be from a 2400, not a 2000 car)

Thanks,

-Richard
gaetan fourez
Posts: 15
Joined: Thu Nov 28, 2013 4:24 pm
Dino: Fiat Dino 2.4 Coupe

Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by gaetan fourez »

Hi Richard,
At test of a 2.4l coupé before buying it, vibrations occured in a similar way except vibration occured mainly and at a maximum between 50 and 90 km/hr. The seller changed the gear mount before delivery and it is ok. I am not specialist but maybe that experience can be of help. Good luck as i understand your frustration, Gaetan
Georg
Posts: 198
Joined: Thu Jan 02, 2014 6:55 pm
Dino: Fiat Dino 2.4 Spider
Location: Germany

Re: Fiat Dino 2400 Coupe - drivetrain vibration

Post by Georg »

Hi Richard
Since January 2014 I have also a Fiat 130 that suffered from very strong drivetrain vibrations. The prophaft is identical to the propshaft of the FIAT Dino Coupé 2400 except for the length. The 130’s propshaft is about 5 cm longer.
Last week I have taken the 130’s propshaft to ELBE Gelenkwellen Service GmbH at Köln (Cologne) www.elbe-gmbh.de to have a complete refurbishment and balancing. I am very happy now since the vibrations have been eliminated completely by Elbe’s treatments.
The major problem was the front section of the propshaft. As the previous owner obviously never greased the front section there was significant wear of the indention (see my photos in earlier post). The front section is no more available. In the late 1990s GKN had them on stock, but they are sold out now. However, ELBE managed to eliminate the wear. They also replaced the universal joint and the ball bearing. The price tag was significant (EUR 520) but the result is convincing.
My recommendation is: send the complete propshaft (front and rear section) to Elbe. Their experience is sound; they will return a zero vibrations shaft to you. Should the bushing in the front section need to be replaced I would borrow my last one to ELBE so they can copy it. I am not sure if these guys at Elbe speak any English, however, I would help as a translator if necessary.
Georg
Post Reply