ALFAGTV6.COM

hi guys, i have just changed out propshaft donut (what was left of it) *see pic.
and i went for a spin to checking for any vibrations and all was great, no vibrations all the way across that sweet rpm range but then i went for a nother ride just now and on my way back (was only a 10 km ride) i noticed a clunking noise intermittantly when not accelerating between 1300 and 2000 rpm, its not very load and the donuts all still look perfect. what else could it be? could i have assembled the propshaft wrong? in which case how could the vibration only start some time after fitment?

see broken bits of original on left, could this have warped my propshaft causing the strange noise?

Check for transmision mounts, if they are not good the transaxle will move up and down with the load and might hit the bump stop.

okay update on this. im really confused, the propshaft noise increases proportional to the speed im going, ie at 20 its wump wump wump then at 60 its just a fast thud and 100 its a whir. also i noticed that if i turn very slightly to the left the sound goes away aswell as when i hit a small bump or similar dip. i can also feel the knocking very faintly though the steering wheel and through the tpropshaft tunnel, but inspection of the fron coupling reveals no sign of anything rubbing against it. please help!

Ok to try isolate this more then get up speed say 90km/h and while its vibrating then
1) push in clutch let revs drop but keeping speed over 80
2) put in neutral clutch out revs drop
Also check while car is standing still rev it up slowly in neutral and put hand on the tunnel nd check with
1) clutch out in neutral
2) clutch in and in gear

Did you split prop at all in centre , did you remove rear coupling when you took prop out .?

Hi Kevin have done all the following already and results are as follows:
1) push in clutch let revs drop but keeping speed over 80

thunking noise stays there

2) put in neutral clutch out revs drop

thunking noise stays there

Also check while car is standing still rev it up slowly in neutral and put hand on the tunnel nd check with
1) clutch out in neutral

no rattle

2) clutch in and in gear

no rattle

i think it must be wheel related (bearings?) due to the fact that the rattle comes from the front of the vehicle where the only part of the car that is directly related to forward speed is the tyres. Prop rotates at engine speed not road speed, and engine is not the source of the rattle or itd be there at idle. could it be a bad wheel bearing? the front right of the car rattles on bumps a fair bit and slews over on rough roads, it also makes a thudding noise whenevr i hit a bump on right. but theres not play or shake on the tyre when i jack it up.

I did split the prop in center but made sure alignment was correct by marking, the first ride i took there was no vibrations, the vibrations only came about 40 km later when i ran her up past 130 at 6000 in each gear to 3rd would that have knocked something out of sync?

A couple of things to check also;

Rear top of the muffler hitting the bolts on the transaxle yoke.

Did you remove the yoke from the transaxle? If so check the nut for proper tensioning.

David

Hi David
ill check that yoke on muffler suggestion, but no i did not drop the yoke from the transaxle, im also certain the noise is coming from the front of the vehicle.

From you description you can rule out prop as vibration is still at high speed but yet prop is at idle when you put clutch in testing .
So it could be if you think front
- loose wheel
- loose wheel bearing
- loose caliper - but that would shudder under braking
However vibration does transfer from rear and possibilities could be
- chipped tooth on pinion which you can check by jacking car of ground and spinning wheel by hand and you will pick up whine or drain gearbox oil which you will then find small pieces . I know this from experience and drive about 200km with broken pinion tooth .
- check side shafts and rear disc have not come loose
- finally change your tyres around .

If you switch engine off at 80kmh when vibration is high ( don't take key out ) is their still vibration . Broken ac pumps , alternators etc can lead to vibrations but you will hear noise first .
Was this only after you worked on prop ?
Check clutch pipe and hand brake cable around rear coupling as well .

yeah, i thought wheel bearings too, but i jacked up each side and shook the wheel to see if there was movement and it was all sweet, no shake at all! could the torsion bar be rubbing on something which when i turn stops? i looked for points of scraping and such that would explain this but found none.

one other thing, before the knocking noise became apparent there was a kind of knock noise that came when i steered left or right some amount, a kind of thunk. that sound is gone and as mentioned before now the sound only goes away when i turn left!
i dont think its a broken pinion tooth as the sound would remain even when i corner then wouldnt it?

I checked the side shafts and discs immediately, but when i put the handbrake on and pushed the vehicle there was no play.

clutch pipe and cable are okay.

the car still makes the noise with the engine shut off, i dont think its AC or any other belt driven thing as they are easily visible and all seems fine.

the vibrations only came a few km after the prop job, (+/- 40 km) i never had a chance to drive the vehicle before that as the donuts were destroyed when i bought the vehicle.

found the problem! was a loose front left tyre, all the lug nuts looked tight... but they werent, im very pleased and somewhat embarassed

Ha ha atleast you found it . It was at top of list on the front section of car . Just relieved it never came off .

yes it was a bit of rookie one by me i must say!
it was pretty close to coming off actually...