vibrating driveshaft

Gilles · #1 (**permalink**) 10-05-2006, 02:14 PM

I removed the driveshaft to swap engines on the Milano and was very careful by marking everything up so I could reassemble it in the same way.

I let run the engine at idle for a few minutes before installing the pinch bolt, I did not remember if this bolt had a washer or not but I put it back using a washer

However, now I have a slight vibration across the entire rpm range and I was wandering if by loosening the bolts/nuts on the front rubber donut letting it run for a few seconds would help or not.

Is possible to balance the driveshaft without removing it from the car? Do I have other options?

Thanks in advance,

Gilles

Murray · #2 (**permalink**) 10-05-2006, 02:29 PM

Gilles my Gtv6 driveshaft does not have a washer on the pinch bolt.I doubt that this is the source of your vibration unless you used a very heavy washer.When you removed the shaft did you disasemble it ?
One possibility is that when putting it back in you didn't get the spherical bushing on the nose of the shaft properly seated in the flywheel.In your situation I would pull it again and make sure the front bushing is well greased and slides into the flywheel properly.When you reassemble leave the pinch-bolt loose and also the two nuts that fasten the centre bearing support to the body.Start the car and rev it a bit and then tighten everything up.If you still have a vibration it can be reduced using hose clamps as balancing weights but hopefully you won't need to.Another important thing to check is some cars have spacer/washers between the rear motor mount arms and the body.I believe that these serve to help allign the driveshaft front-rear.If your car had these make sure you put them back.

**AR4me** · #3 (**permalink**) 10-05-2006, 04:03 PM

I don't recall a washer on the pinch bolt either. Hmm, vibration across entire RPM range...? I think that a slightly out of balance drive shaft usually has vibration in an RPM range, e.g. 2500-3000. Did everything go back together smoothly?
Jes

Gilles · #4 (**permalink**) 10-05-2006, 04:43 PM

Jes; Yes it seemed that the bushing went in all the way.
Murray; Do you meant that I should loose the pinch bolt AND the two nuts on the center support, then running the engine before tightening them again?
Gilles

Murray · #5 (**permalink**) 10-05-2006, 04:49 PM

Gilles Yes exactly.Loosen the centre-support nuts just enough so that it can settle into place when the shaft is turning.If you can safely lie under the car while the shaft is rotating you may be able to see where the vibration is most pronounced.

**kredden** · #6 (**permalink**) 10-06-2006, 06:13 AM

Gilles,

One other possibility, you say you swapped engines? If that is the case then I've heard (although I don't know if it is true or not) that originally the driveshaft and crank were balanced as a single unit which could then cause an out of balance situation if you are using a different crank/driveshaft combo.

Personally I find it hard to believe that they were not balanced separately as it is far more common to take the driveshaft out and muck with it than the entire combo!

I have a mixed combo in my Verde right now (164 engine with my Verde driveshaft) and I do have some vibration issues but no worse than the original combo :-). When I installed it I did the whole loose pinch bolt & hanger bolts trick but it didn't make much difference in mine (there is no washer for the pinch bolt on either of my driveshafts either).

I do have a question on the hose clamp trick...do you just put one on, start up see if the vibration is still there, if so move it around a little and repeat? My spare driveshaft does have a clamp on it and I've been meaning to ask :-).

Kevin

Murray · #7 (**permalink**) 10-06-2006, 07:17 AM

Kevin the "high tech." hoseclamp/driveshaft balancing procedure is as follows:

Jack the car up and support it securely on jackstands so that you can lie under there.Make sure you have good lighting as you can only see parts of the driveshaft as it's hidden behind the exhaust,heat shield etc.Once you start the engine you need to use either a white marker of some sort or a screwdriver to scratch the black paint.Slowly allow your marker to approach the driveshaft surface as it rotates.The marks which are left on the surface will show the "heavy" side of the shaft.The heaviest part of the hoseclamp is the screw so you want to position it such that it is opposite the marks on the driveshaft.On my car I ended up using two clamps to provide enough weight to counterbalance the shaft.Don't forget that there are weight plates welded onto the shaft at the factory and you don't want your screwdriver to contact these while the shaft is spinning

Gilles · #8 (**permalink**) 10-06-2006, 06:32 PM

I had been puting closer attention to the drive shaft vibration issue and I had noticed that 'sometimes' when the car is cold does not always vibrate as much.

I planned to dedicate the weekend to try to fix the vibration problem, but since I removed many things during the engine swap it just crossed my mind that maybe the engine could be causing the vibration, perhaps one of the hoses into the plennum is on the wrong place but the book is not too clear.

Also I could not adjust the idle high enough so I simply unscrew the butterfly detent screw to increase the rpm and readjusted the idle using the idle nut, all this without adjusting the TPS, earlier today someone posted that adjusting the TPS cured the surging issues which I also have (barely noticeable)

Perhaps I should start at square one with the FI 101 and start from scratch adjusting everything the way it's supposed to be adjusted.

Any suggestions where to start?

Thank you in advance, Gilles

slyalfa · #9 (**permalink**) 10-06-2006, 06:51 PM

just as a note I had the pinch come lose one time and that caused the drive shaft to whip and it bent the drive shaft! I took it some where local(do not rember the name) and all new rubber parts and had them balence and unbend it and it has been many years and 3 or 4 flex joints latter and it is still is good.

**kredden** · #10 (**permalink**) 10-07-2006, 05:49 AM

Thanks for the hose clamp how to! Makes pefect sense, gets a little tricky (at least for one person to do) if it only happens at specific revs though :-).

Gilles, it probably is worth starting from scratch and go through everything, if you haven't already done it I'd recommend Greg's page: http://www.hiperformancestore.com/L-jetronic.htm.

After re-reading my previous post I think I was writing while sleep deprived...what I meant was that the crank and the flywheel are balanced together, not the driveshaft, which of course makes no sense. In my engine swap I did have to change flywheels so this could be throwing mine off a bit as well.

Kevin

**AR4me** · #11 (**permalink**) 10-07-2006, 08:12 AM

Quote:

the crank and the flywheel are balanced together...I did have to change flywheels so this could be throwing mine off a bit as well

**kredden** · #12 (**permalink**) 10-07-2006, 11:01 AM

That's what I would have thought, the multi part balancing heard from at least a couple different people might just be an Alfa urban legend

.

The other one I hear mentioned and written about so many other times is with the different weight nuts, bolts or washers (don't remember which) to balance the driveshaft. I can perhaps believe that there is some slight variation in the weight of each of them and that moving them could cause some minute changes but not enough to notice. Opinions?

Kevin