[Hjulen]

I am having a problem that has only shown itself recently on my '84.

When I am on the highway, and especially while in 5th gear approx 3000 or so rpm I get a very pronounced vibration through the car. It disconcerting enough that I down shift to 4th (engine now approx 4000+ rpm) and the vibration goes away.

Now the car has 83,000 miles on it and to my knowledge the driveline has never been serviced though the previous owner has the clutch replaced at some point. I have not had this problem until recently (I have owned the car about 2 years).

Now before I undertake a very time consuming and expensive replacement of the guibos and bearings, I have also read on Greg Gordan's site about something called a transaxle snubber that could be causing some vibration. How can I tell if that is the case?

I want to be sure I am not going to over do it, as the navy doesn't give me much time, space, or money to mess around too much.

Thanks,
James

 

[sh0rtlife]

get it up to speed put it in Neutral and let the clutch out and see what happens....also try verifying that the same RPM causes it in ALL GEARS ....try to verify its not a speed issue(tires/wheels)

 

[nofiat]

It may be that your donuts are shot. I had the same problem about 15 years ago with my Alfetta and replaced the rear donut with one from International Auto, but the problem persisted. I finally went to a local dealer and got the CORRECT replacement part and the difference was amazing!

 

[Hjulen]

Haven't had a chance of getting the car up to speed, been chasing a FI gremlin (either thermo time switch or AAV). I noticed that I could rev the engine in neutral at a stand still and there was no vibration at the specified RPM. This leads me to think that the drive shaft isn't out of balance.

What should I look for visually on the donuts or is this going to be obvious?

I can get access to a lift to replace the donuts but it definitely would be the biggest task I have undertaken on the car. Are there a lot of "while I am in there" items when replacing donuts such as the shaft bearings and such?

 

[AlfaTango1]

Donuts and or drive shaft out of balance if it has been removed before is my guess.

 

[nofiat]

Look for cracks. If the donuts look good, then research whether any of them have been replaced, as they may have been replaced with the wrong part.

As I recall, there were at least three different types of driveshaft donuts for the Alfettas. The donut for my model car was incorrectly identified by International and I lived with serious driveshaft vibration for two years before wising up and tracking down the correct part.

 

[mjr]

drive line last!! get your wheels checked for true running, and balanced. Only after move to the prop shaft.

 

[Randal Harris]

Drive shaft would be my LAST choice for the problem. The drive line is tied to engine speed regardless of the gear your in. If the vibration happens at 3000 rpm in 5th but not in any other gear then it would seem to be road speed related and not engine speed related. Wheel balance issues tend to show up at this speed (60 mph +/-). Also, bent wheels and out-of-round tires. Delaminating tires or excessive tire wear caused by out of alignment front suspension. Hunk of metal missing from a disc brake rotor. God forbid, it could be transaxle related (5th gear) or in the drive shaft joints. Last resort could be transaxle mounts or something about the donuts that doesn't like the combination of the torque necessary to maintain 3000 rpm while running against the resistence of 5th gear.

 

[Alfissimo Int.]

I am having a problem that has only shown itself recently on my '84.

When I am on the highway, and especially while in 5th gear approx 3000 or so rpm I get a very pronounced vibration through the car. It disconcerting enough that I down shift to 4th (engine now approx 4000+ rpm) and the vibration goes away.

Now the car has 83,000 miles on it and to my knowledge the driveline has never been serviced though the previous owner has the clutch replaced at some point. I have not had this problem until recently (I have owned the car about 2 years).

Now before I undertake a very time consuming and expensive replacement of the guibos and bearings, I have also read on Greg Gordan's site about something called a transaxle snubber that could be causing some vibration. How can I tell if that is the case?

I want to be sure I am not going to over do it, as the navy doesn't give me much time, space, or money to mess around too much.

Thanks,
James

I agree, wheels being true could do this. Check your gear box mounts, there are 3 in all.

Also start simple as mentioned. make sure wheels are properly balanced. Are your tires good? Check for true wheels.
There are a slew of things that can give vibration.

Is there a specific side, front or rear that you can feel it?

Any odd noise when it vibrates?

Could be a propeller shaft support or one of the flex joints.

Could be as simple as a tire being a bit low.

Good luck
Jason

 

[AR4me]

Check your gear box mounts, there are 4 in all.

Uh, only three transaxle mounts on a 116. Two fronts and one rear.

I agree with the people saying that drive-shaft is an unlikely culprit if vibration is not present at the same RPM regardless of gear. Drive-shaft spins at engine speed: a drive-shaft induced vibration is typically present at the same RPM regardless of gear, including neutral.

Jes

 

[Hjulen]

An alignment issue or wheel balance issue would make sense to me. I believe before I got the car there was a repair done to the front passenger side shock tower. Ed at Difatta brothers said that the front end alignment may be affected by it.

Another thing I noticed was that it seems the car has quite a bit of camber...perhaps more than I think it should have.

The next step I think for me will be to get the alignment checked then. Should I be worried about a random shop around here doing it? Or is the Alfa gonna confuse em too much.

 

[Alfissimo Int.]

Uh, only three transaxle mounts on a 116. Two fronts and one rear.

I agree with the people saying that drive-shaft is an unlikely culprit if vibration is not present at the same RPM regardless of gear. Drive-shaft spins at engine speed: a drive-shaft induced vibration is typically present at the same RPM regardless of gear, including neutral.

Jes

Uh, yeah I know.....typo! Thanks LOL!

 

[Hjulen]

I had the car out on a 200 mile trip this weekend.

I am becoming increasingly doubtful that it is related to the driveline OR wheel balancing. The best I can describe the condition is as a "shudder" and there is what I feel is some power lose associated with it (this could be imagined).

There are times were I will drive around same speed, same gear and there be no problem at all. It seems to manifest itself independent of gears, but usually always around 3000 rpm. If I put the car in neutral and let it coast or if I rev it in neutral then there is no shudder.

I am wondering if a vacuum leak could cause these problems. Bad motor mounts?

This could be unrelated but I had problems starting the car the other day. Cranking but no ignition. Spark seemed good. That Problem went away and hasn't come back since.

Thanks

 

[mjr]

it sounds like it could be a defective clutch or gearbox problem then, it could also be a failing propshaft centre bearing too. I think you are in for a long road my friend, you have no choice but to start front to back and go through all of it. Drive line vibrations are bad news and are a ***** to find. just hop e that it is the propshaft donuts, becasue that will be easy enough to sort out.

 

[Randal Harris]

If the shudder goes away when you put the car in neutral and coast it is not likely to be suspension related. The suspension does not know the difference between under load or coasting. However, I would still have the alignment checked because of the previous damage. Also, have the alignment shop look closely at the tires for unusual or excessive wear or delamination. I had similar symptoms on my pickup truck and it was a front tire starting to come apart and the damage to the tire was better felt by running your hand over the surface of the tire than by visual inspection.

Otherwise, check the three engine and three transaxle mounts. They might be giving these symptoms under load but not when rev'd out of gear. Clutch? Again, the entire clutch is attached to the driveshaft and turns at engine speed, not road speed so I would put that further down on the list of possible causes. Out-of-balance clutch and clutch bearing slop would seem to show in every gear and even when rev'd out of gear.

Driveshaft center bearing is possible though I'm unclear on how the torque of spinning in (shudder) or out of gear (no shudder) might effect the shudder.

QUESTION: Is there anything about the fuel injection system that might be causing this? Getting the engine to rev to 3000 rpm under load is quite a bit different than doing it without load. Partially clogged line or injector? Defective piston inside the fuel injection pump? Is compresson within the engine ok? Good spark plugs (not missing under load)?

Randal Harris
'78 Sport Sedan
'62 & '67 Spiders