A dozen ways for an alfetta driveline vibration...? - Alfa Romeo Bulletin Board & Forums
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post #1 of 51 (permalink) Old 12-17-2017, 09:08 PM Thread Starter
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A dozen ways for an alfetta driveline vibration...?

So in the "epic Journey" thread I discovered a vibration here's the list and a question.

The question: Is there any difference between the GTV6 clutch housing on the transaxle and the one on the 1.8 or 2litre transaxle or even the Twin Spark. Clearly I need a replacement but am unsure if I can just rip one off any old transaxle.

10 different ways.

Please take this all with a pinch of salt. That is don't rely on my limited experience.

This needs some introduction. A vibration/noise varies wildly from a slight metallic tinkling noise to a car shaking vibration that feels like your car is about to come apart, because it is.

The mild tinkling noises come from the clutch spring making a small noise as the clutch assembly itself rotates at low speeds. The spring acts a bit like a bunch of tines. As the flex they "tinkle". Presumably this is a reflection of some other process allowing the clutch to move about. The huge vibration noise is the drive line moving in a fashion resembling a skipping rope.

Sources from front to back.

1. Your engine mounts are no good so the engine moves around creating a vibration. Check the engine mounts.
2. The front Donut is cracked. This is the floor shaking whenever you rev the motor.
3.The middle donut is cracked. Same as 2.
4. The Prop bearing holding up the drive shaft is dead.
5. The prop support is sagging
6. The rear donut is cracked.
7. The Yoke is loose on the Clutch shaft
8. The bearing holding the clutch shaft is loose or "reamed"
9. The Clutch assembly is out of balance.
10. The bearing at the back of the clutch is dead.
11. The Clutch housing is not tightly bolted to the mounts
12. The mounts are worn.
13. You have Alfa 75 Mounts (which are too high) installed in a GTV6

My GTV6 has numbers 5, 7, 8, 9 (how do I know?), 11 (bolt holes have worn through due to vibration), 12, same as 11, and possibly 2,3,4 and 6. Other than that: it seems fine...

Have I missed any? Are any completely off? Does the clutch assembly really need balancing? If so how?

Merry Christmas. I envy those of you who are in the Northern Hemisphere where it is winter and the whole festive season makes sense unlike here where it was 38c today and it gets dark at 9pm.
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Last edited by Millsy; 12-17-2017 at 09:31 PM.
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post #2 of 51 (permalink) Old 12-18-2017, 12:43 AM
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Tail shaft Vibration

Your post made me LOL. Thank you.
Pretty sure the housings are the same. I'm sure I will be corrected if I am wrong.
I can think of a few other issues that may cause vibration.


Bent tail shaft.
Loose flywheel.
Horrific out of balance bottom end engine assembly.
Your entire car is bent.

lol
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post #3 of 51 (permalink) Old 12-18-2017, 02:10 AM Thread Starter
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Fabulous! I will add this to the eventual list!
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post #4 of 51 (permalink) Old 12-18-2017, 05:25 AM
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I think that there are two styles of clutch housing for the different (push or pull) clutch release methods.

Ed Prytherch
79 Spider
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A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #5 of 51 (permalink) Old 12-18-2017, 05:54 AM
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I should never be trusted with diagnostic issues. But, I'll pass along something I was told by a very good ALFA mechanic long ago---

If the drive shaft comes out, and/or is disassembled, the components should be marked to match their exact positions when reassembling, BEFORE tear down. As the drive shaft is balanced with weight patches at the factory, if the two halves are not in that alignment when they go back together the balancing has been compromised. And likely made worse than if it weren't balanced at all.

I'm prepared to be corrected if I've mis-stated that. Best of luck in solving the vibration.

Peter
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post #6 of 51 (permalink) Old 12-18-2017, 06:19 AM
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Well... The latter seems a bit of a myth. Nothing stops the factory from balancing the halves apart from each other. And if they are fine balanced as a whole, with the giubos on, that means that replacing the giubos will also compromise the balance since the new ones are never known if perfectly straight or not.
It happened to me twice that a 1/6 piece of a donut shot off, once from the central one, and once from the rear one. In fact, the vibration was not that dramatic. At least I could drive it comfortably a few days after, not over-revving the engine, of course. It was the centering spherical bush that really spoiled the ride.

1975 Alfetta; ex 1973 Spider; ex 1984 Alfetta Quadrifoglio Oro
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post #7 of 51 (permalink) Old 12-18-2017, 06:59 AM
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I think what I was attempting to say is: the front and rear portions of the drive shaft are balanced as one unit. If those two halves are reassembled differently when the center donut is replaced, you may have just disturbed the balancing. Hope that sounds more accurate than my first stab at it. If the original shaft assembly required little to no weights to bring it into balance, probably not as crucial. If the shaft initially required a lot of tweaking to bring it into balance at the factory, then that theory has a bit more sway, I would think.

If that still sounds off-target, I'm braced to be set straight. I found that out the hard way from one local mechanic who said he could work on any car. Turns out he failed to include ALFAs. They had to try every possible variation in finding the right combination again. After that, I decided to drive an hour and a half each way to Albany to find a mechanic who was familiar with all the quirks on these cars. It was worth the extra 3 hours on the road.

Peter
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post #8 of 51 (permalink) Old 12-18-2017, 08:27 AM
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Sound practice is to mark and reassemble all multi piece drive shafts in EXACTLY the same way they came apart. Yes its true that most of are cars have been messed with but sound practice is sound practice.

If you can locate a drive shaft shop that can balance the driveshaft as an assembly - then that's the way to do it. I fabricated tooling to do mine this way at my local driveshaft shop. But I spin it to 7000+ RPM all the time for long periods of time on the race track.

I have broken some drive shafts in racing and sourced used ones then refurbished them along the way. I have come across 3 sets in that time that had bent tubes so that is a thing as well. I have seen the center yoke assembled incorrectly phased multiple times and almost all of them have had the bolts joining Giubos inserted the wrong way.

Remember when it comes to driveshaft OCD is your friend.

Greg
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1972 Berlina Vintage Racer, 1987 Milano Platinum (LeMons Car), 1982 GTV6 EP Race Car, 1974 GTV Vintage Race Car, 2012 VW GTI stage II, 1966 Corvette Coupe 327-350, 2007 Triumph T100 Bonneville. Dearly departed: 1971 Fiat 124 Spider, 1983 Saab 900 Turbo, 2004 Saab 9-3 Aero, 1995 BMW 540i Sport, 2014 Audi A4 (swamped)
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post #9 of 51 (permalink) Old 12-18-2017, 08:27 AM
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Even if so, it doesn't mean it has been always assembled the right way before you bought it (if you're not the first and only owner; congratulations if you are!).
FI, I have paint marks on mine but now I doubt they're put the right way, at least those on the yoke on the splined end of the front part. And yes, there are vibrations. I'm not quite sure but should the yokes be aligned, as they are on the rear part? Mine are not. I mean, if you look along the shaft, you'd see them at a little angle to each other, not at 60 deg. or so. If they should, this could also be a clue that someone made a mistake before.

And sorry if my post sounds insulting; of course, I didn't mean that.

1975 Alfetta; ex 1973 Spider; ex 1984 Alfetta Quadrifoglio Oro

Last edited by Q.V.; 12-18-2017 at 08:40 AM.
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post #10 of 51 (permalink) Old 12-18-2017, 08:31 AM
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Quote:
Originally Posted by GregSef View Post
Remember when it comes to driveshaft OCD is your friend.
Not only the driveshaft. It's true about nearly everything in these cars! They do forgive, but as you aim at perfection, every slightest detail matters!

1975 Alfetta; ex 1973 Spider; ex 1984 Alfetta Quadrifoglio Oro
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post #11 of 51 (permalink) Old 12-18-2017, 08:31 AM
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No promises that this is correct so buyer beware but here are some of my driveshaft notes: Format a bit screwed up.

Drive Shaft Info Transaxle cars.

Bolt info: Front Giubo use the bolt heads on the driveshaft yoke. The washers are under the nuts. The seal gets installed with the smallest ID facing back.

Middle Giubo all the bolt heads are on the front side. Washers are always under the nuts. The center splined yoke is 60° out of phase with front & rear yokes.

Rear Giubo uses the bolt heads on the yokes and nuts on the Guibos. The washer are on the nuts.
Alfa sometimes used cut down nuts that threaded on top of elastic stop nuts to correct balance.

Caution: there are more than one length of Giubo bolts. Make sure you are using a matched set.

Milano Driveshaft length: front 29.5” – 29.25” flange to flange. Rear 24.3” flange to flange.

GTV6 Driveshaft length: front 28.6” – 29.25” flange to flange. Rear 19.9” flange to flange.
(Fronts are identical)

Driveshaft tubing: Front tubing is 70mm OD (2.75”) x 1.5mm wall. Rear is 50mm x 1.5mm wall. Front section tip casting has a 2.645” OD to receive tube.

Split bearings: 22mm OD x 12 mm ID x 11mm wide.
Torques
Front & Rear Giubo’s 40-42 ft. /lbs.
Center Giubo (29-36 ft./lbs.)NG 40-42 ft. /lbs.
Driveshaft center bearing nuts 69-76 ft. /lbs.

Greg
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post #12 of 51 (permalink) Old 12-18-2017, 08:37 AM
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Quote:
Originally Posted by GregSef View Post
The center splined yoke is 60° out of phase with front & rear yokes.
Thanks Greg! That's what I meant, exactly. My sense of symmetry suggests it's either 0 or 60 degrees... And if I remember correctly, the splines are an odd number, so you can slide it the right way in only one position. Otherwise it wouldn't be set at exactly 60 degrees.

1975 Alfetta; ex 1973 Spider; ex 1984 Alfetta Quadrifoglio Oro

Last edited by Q.V.; 12-18-2017 at 08:39 AM.
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post #13 of 51 (permalink) Old 12-18-2017, 10:56 AM
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Add another source of vibration to your list: the splined pinch yoke at the front may be loose, or worn, or both.

The driveshaft(s) may be slightly bent, on early cars that do not have the removable center support.

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post #14 of 51 (permalink) Old 12-18-2017, 11:40 AM
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Quote:
Originally Posted by Q.V. View Post
And sorry if my post sounds insulting; of course, I didn't mean that.
Not to worry. I merely took it as a correction to my incomplete thought. I think, between us, we may have helped clear up the confusion I had put out there.
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post #15 of 51 (permalink) Old 12-18-2017, 01:15 PM Thread Starter
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Oh ! I forgot about the drive shafts being bent or unbalanced... so Alfettaparts2 adds

14. Bent tail shaft.
15. Loose flywheel.
16. Horrific out of balance bottom end engine assembly.
17. Your entire car is bent.

I think 17 may have some indicative body crumpling... while 16 would likely be rather short lived.

as part of this process I spoke to an old Italian (now Old Italian Aussie) who is adamant that the clutch assembly itself (shaft, flywheel, clutch) as a whole can be out of balance. Given how nicely my car drove when the vibration wasn't occurring (i.e. it was intermittent but vicious) I don't think this is an issue for me. So is number 9. above a thing? Does it occur?

I will be collecting my clutch housing from the welders (who couldn't weld it without a sample of the metal) today and will compare it with some others later this week. I will let you know.

Do we have any advances on 17?

Greg your info is pure unalloyed GOLD! I would have reinstalled the washers against the nuts... Its long past time I bought a decent torque wrench...
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