My 4th series B20 has a vibration, that is steadily getting worse. It starts at about 3500-4000rpm in every gear , wich limits the useable top speed to about 100-110 kph. Apart from that, I don't think it is very good for the mechanical health of my car to keep on driving it like that. My guess is that it has something to do with an inballance in the propshaft (wich turns at engine speed), that sends a vibration trough the whole bodyshell, you feel it first in your feet. Does anybody out there has any experience with this problem and/or an possible solution?
Greetings,
Koen
Aurelia propshaft vibration
-
Randy Adams
Re: Aurelia propshaft vibration
Remember that the clutch and rear flywheel must also be balanced, preferably in unit with the driveshaft. A shop familiar with the Alfa Romeo arrangements from the late 1970s and 1980s should be able to cope with the balancing work.
If the flexible couplings are deteriorated, they will also cause vibration.
If the flexible couplings are deteriorated, they will also cause vibration.
-
Geoffrey Goldberg
Re: Aurelia propshaft vibration
There is a lot of work that has been written and done on this problem. Have you looked in the manual, assembled by Paul Mayo? Along with what you may find there, here are some thoughts:
Typically, the first major problem is bad probshaft balance - they wee factory aligned and balanced very carefully. If the shaft has been taken off and put back out of "order" (not lined up right) then it will be out of balance. Answer: get it balanced. The connection between the front and back parts, plus all the bits, must be maintained as it is when it is balanced. Very critical.
Next, look at the couplings, and the little brass bushings. If they are way too loose, you'll get some flopping around. This is probably not your problem, as it shows up at low RPM.
The shaft should be loose in the center mount. It hunts for its own center, and thus the center mount must allow for vertical play. Again, see the manual. Too foten "experts" tighten this mount up too tight. No good.
Making sure the clutch and flywheel are in balance is a good thing too, as mentioned earlier. Ideally, all the pieces should be done together, but if the clutch and flywheel are in good shape, this probably isn't the first place to look. One way to check the flywheel : disconnect the shaft and see what your motor vibration is like on its own.
Finally, last place to lok (and unlikely, but if everything else doesn't work) - check the alignment of the motor to the trans: the crankshaft centerline should be aligned straight with the centerline of the trans. If the car has been in an accident, or something is really goofy witht he mounts, this can be off, and put the shaft in an angular condition. Not desired.
Most typically, the vibration is due to the shaft not being in balance. Sometimes it can be put back into balance through careful tinkering by a real Lancia pro (in place, fiddling with the shafts) but most times, beest taken off, sent to a VERY good propshaft balancer, who will both make sure it is straight and balanced. I had terrible problems wiht a 4th s. B20 shaft, and we found that the original runout on the shaft was as high as 70 thou of an inch... due to poorly matched alum fittings, slightly worn and eccentric spline mounts, etc. By the end of the balancing exercise, we were down to about 6 thou. Car was smooth.
It can be done. Takes care and attention to detail. of course, the wisest path is to find a real Lancia guru and work with them on this. But hopefully, this hits the major points on this problem for you.
Typically, the first major problem is bad probshaft balance - they wee factory aligned and balanced very carefully. If the shaft has been taken off and put back out of "order" (not lined up right) then it will be out of balance. Answer: get it balanced. The connection between the front and back parts, plus all the bits, must be maintained as it is when it is balanced. Very critical.
Next, look at the couplings, and the little brass bushings. If they are way too loose, you'll get some flopping around. This is probably not your problem, as it shows up at low RPM.
The shaft should be loose in the center mount. It hunts for its own center, and thus the center mount must allow for vertical play. Again, see the manual. Too foten "experts" tighten this mount up too tight. No good.
Making sure the clutch and flywheel are in balance is a good thing too, as mentioned earlier. Ideally, all the pieces should be done together, but if the clutch and flywheel are in good shape, this probably isn't the first place to look. One way to check the flywheel : disconnect the shaft and see what your motor vibration is like on its own.
Finally, last place to lok (and unlikely, but if everything else doesn't work) - check the alignment of the motor to the trans: the crankshaft centerline should be aligned straight with the centerline of the trans. If the car has been in an accident, or something is really goofy witht he mounts, this can be off, and put the shaft in an angular condition. Not desired.
Most typically, the vibration is due to the shaft not being in balance. Sometimes it can be put back into balance through careful tinkering by a real Lancia pro (in place, fiddling with the shafts) but most times, beest taken off, sent to a VERY good propshaft balancer, who will both make sure it is straight and balanced. I had terrible problems wiht a 4th s. B20 shaft, and we found that the original runout on the shaft was as high as 70 thou of an inch... due to poorly matched alum fittings, slightly worn and eccentric spline mounts, etc. By the end of the balancing exercise, we were down to about 6 thou. Car was smooth.
It can be done. Takes care and attention to detail. of course, the wisest path is to find a real Lancia guru and work with them on this. But hopefully, this hits the major points on this problem for you.