prop shaft vibration

[sudsy]

All things aside..

What is the most common source of prop shaft vibration.??

my situation:
It's not chronic
It diminishes with speed
It diminishes with time/heat.
Its a gentle rumble/vibration..

So I'll get under her and have a poke around, but if i'm pre-informed then all the better.
Issue has been there since day one of ownership, time to get it sorted..
Thing is if I can't see anything obvious, i'd like to know which bits to poke further

Doughnuts or bearing?

I know that this is a long assessed issue, but keen to know what is the MOST likely problem.

I think this ol girl will run forever, even with  a slightly wonky prop shaft, but I'd prefer to get it sorted and with a modicum of info if I need to refer it to my local alfa guy..

Thanks

[carlo rossi]

number of reasons
check all bolts are torqued up
yep I have seen loose ones in my time and look for cracked donuts
or chunks missing sounds like when the donuts get hot they are more plyable
so they smooth out

[sudsy]

Thanks Carlo

I think you might be correct about the temperature and plyability of the doughnuts..as one or more of them may be age hardened, and they are made of rubber for a reason.

[Alfapride]

Few other things to consider
Condition of centre bearing
Engine mounts
Prop shaft alignment
If it's been installed re installed incorrectly in the past it may need a balance

[carlo rossi]

yeh thats a difficult one
i have just spent 12months do my own version of balancing
cost me 1 back 12 headaches ,52 weeks of my life and yes im happy now
all becasue the guy that took out my shaft didnt mark it up and photo everything

[Craig_m67]

Cherry, the new lacework of rust that is a GTJunior also has a rumbly driveshaft.  It's worse when she's been sitting (often) but gets less noisy with drive time/heat etc.

I originally thought it was out of balance.. got a quote for that and decided I could live with it

On reflection, I don't think it's balance - I mean why would it be out?
My current thinking is; centre bearing, u-joints and the donut
Apart from the donut, everything else is very likely original and as such worn as fuck

All things the DIY can do.  The AlfaBB had some interesting info on the u-joints, suggesting some replacement parts were not quite in spec these days.  All of it can be obtained from the usual suspects (classic/AH) though, so I'd just give them the model details and buy a kit

I will do the Duetto's drive shaft if she ever comes home.. Cherry can rumble on


EDIT.  I should add, i've answered this from the perspective of a 105 drive shaft, not a 116 which is a completely different animal (spins at engine speed all the time).  I'd be checking the donut stat.  There's lots of messy pictures available of the hazards that can occur if they let go.  Apologies for the detour into an earlier, different model

[sudsy]

Great input from everyone

I thank you all..

Oddly enough, as things got warmer then hotter today, the vibration actually got worse.
It got to being borderline unpleasant.

I'll check all that's been suggested.. and mark everything up as I'm checking..

....It sounds as if that's quite crucial if you don't wish to make matters worse....

Rookie question: Am i at risk of amplifying and adding to repairs if I continue to drive on a vibrating prop shaft?.
In as much as, would the current out of balance potentially lead to the tearing at and ruining of other prop shaft components?

[bazzbazz]

Rookie question: Am i at risk of amplifying and adding to repairs if I continue to drive on a vibrating prop shaft?.
In as much as, would the current out of balance potentially lead to the tearing at and ruining of other prop shaft components?

Yep, you guessed right.

[poohbah]

Just posting this as a gentle nod to the joys of rubber drive train components (so +1 to suggestions they should be high on Sudsy's checklist).

When I bought my '81 GTV four years ago, I was assured the donuts had been replaced fairly recently.

This was the reality (my mechanic reckoned the prop shaft hadn't actually been touched in over 30 years.)

I still love her...

[sudsy]

@ poohbah
That looks catastrophic..

Good news is rego ran out today so cant be tempted to drive the sedan anymore avec ill prop shaft..

I'll get it all sorted before putting more rego onto it..

[poohbah]

Best of luck with the propshaft and rego sudsy. Lucky for me I caught it about a week after I bought the car.

[carlo rossi]

Lets just start with what I think of the tailshaft
f#$%^&**((()))ing
yep almost every time I have asked that question
how are the donuts? they always reply "just had them done "
well there is a date stamp on the beasts and like all rubber
even if not used it goes off so if the donuts are over 15years
they will probably need replacing , they go hard

NOW the bad part
when you take it out mark everything all the bolts categorise so they go back exactly
the position of the tailshaft to the body measure at the engine rear mount and put back exactly
if you split the shaft and change bearing 2 things if its a post 1983 model
buy the bearing first its a 55 mm not the 52mm of the earlier Bloody hard to find
ea spares has them I think
mark how the shaft came apart and the spline and put it back together exactly not almost
or you have then balance the beast
p[s there seems to be a never ending model version change on these things so don't buy the donuts until you can see the ones on there and their numbers
Oh by the way this is for the 4 cyl not the v6 it has only 1 arrangement

[tpalfa]

I had a vibration on my GTV6 which was hard to track down. A mechanic had used a BFH to get the shaft back in and had cracked the metal sleeve of the locating bush that's on the end of prop shaft inside the front donut. After it warmed up at high revs it was terrible.

[carlo rossi]

i believe they are all split to get them on and off
i hope this did not cost you much

[tpalfa]

i believe they are all split to get them on and off
i hope this did not cost you much

The broken part was one of these:-

https://www.alfa-onlineshop.de/fuehrungsbuchse-nebentrichter-kardanwelle-neu-alfetta/gt/v-75-rz/sz-14096

it was well and truly smashed. Didn't cost me more than I paid for the original work - which was to replace two donuts and the centre bearing.