105 drive line vibration above 100mph

Gents & Ladies:
My GTJ with TS is silky smooth at 80mph but starts to vibrate above 100.
Heavy duty doughnut fitted, new UJS & propshaft greased, wheels are balanced.
What is your experience, do the drive rubbers get excited at these speeds?
Anybody been up to 130 140? the motor on mine seems to have some left to go at 120.

Of course all of the above was completed on a track day.

Have a read here:
Alfaholics Front Propshaft Conversion Kit

Yes Im aware of that kit but was trying to avoid the expense.
Q: to all 105 drivers. Do you suffer similar vibration at such speeds?

I don't, but I avoided the heavy duty doughnut as I was advised that it exaggerated any inbalance in the transmission. I haven't got the oomph you've got but up to 100 it's fine.

My Spider has a 100% original drivetrain etc. and the couple of times I have been to such speeds I've never had any untoward vibrations anywhere.

Nothing undue to report here either, I suppose it's going to be subjective as to how much vibration you would expect at those speeds. It's bound to be worse as there is so much energy flying about.

Daft question but is it just simply a wheel balance problem?

Hello,

If t's the wheelbalance you should feel it in the steering wheel, it get more and more loose.

What about one or more of your wheel, they could damage or even one of your axel, actually even a wheel bearing...

try to locate the source,front or rear.

Cheers

Andre

Hi,

Had the same problem some years ago and also had all the parts you mentioned replaced but a low vibration at certain speeds. A very old Alfa mechanic here in Malaysia finally traced it down to the propshaft support and the tremors disappeared.

Inexpensive and it worked, you might want to check it out.
Good luck

Yes could be the centre prop shaft bearing, I thought I read it had been changed, but you just did the do-nut so if it's an old bearing it might have too much play.

A rear wheel balance problem tends to be felt through the chassis (and your bum!) rather than the steering wheel, so it could still be that IMO.

Wheels are fine
Center brg is new
UJ's are new
Gearbox overhauled by me
Doughnut is new yet already has witness marks on its surface.

Hi,

Ok ok, it's getting though.

Where do you feel this vibration?

Steering wheel, engine, chassis?

Sound like you have done a lot on your car, engine and gear box mounting are new of course?

Maybe it is just the engine itself which is a bit un balance.
I must say with my spider ( I haven't done much on it yet) when I push to that kind of speed a bit of everything vibrates
But nothing abnormal.
Andre

Before my prop was rebuilt it vibrated around the handbrake. "Everything" was slightly worn but the main thing was one of the UJs was no longer U'ing. It was just a J.

Rear gearbox mount is worth checking as mentioned above.

Everything is new & heavy duty. I notive the center flanges are 180 degrees out so will swap that round. & also check the full alignment through the car. I will post it up when I find the answer. A Chap Erik on the AlfaBB tells me his is smooth at 130mph so I know its possible.
Cheers for all your input.
Ps for those wondering: Its a std twin spark & EFI 2000LSD, 37mpg on unleaded, smooth with great torque. If your thinking of doing the conversion just do it. Super reliable too.
Keith

Just to add my 2p worth, all the moving parts may well be new, but has the propshaft been balanced as a complete assembly. Replacing any 1 of the parts in the prop. assy. could take it out of balance, so having replaced every joint and bearing, the chances of the assembly being out of balance is very high.

The shaft is balanced in the factory, all new parts are symetrical and cannot affect the balance me old mate.

If you've gone to all the expense mentioned so far, for what it would cost to have it checked, i'd get it done. Something that is possibly somewhere between 30 - 40 years old may have been OK when new, but all manner of things could have happened to it thru its life.

Originally Posted by crashmctavish

The shaft is balanced in the factory, all new parts are symetrical and cannot affect the balance me old mate.

Yes it can, if the front and rear shafts are not matched up in the same orientation the balance will be affected.

I swapped them round & it made it worse, so back to the original. Car is laid up for the winter now so It can wait till the spring.