Drive Line Vibration and Guibo Alignment

2063 Views 8 Replies 6 Participants Last post by 1166, Jan 5, 2008

hmacris

Discussion Starter · Jan 3, 2008

Hi All,

I am relatively new at this (20 years old). My family has had and driven Alfas for as long as I can remember. I recently bought an 88 Milano Verde that came with the evo front and rear bumpers. It vibrated horribly until I found out that one of the cylinders was not firing. This solved a lot of it, but there is still bad vibration in any rpms over 2000. I brought it to my local alfa guy who looked it over and said the driveshaft may have not been replaced correctly the last time the service was done and that it is most likely coming from that. How should the rubber guibos be in relation to the driveshaft? I think it may be coming from the middle guibo...

Any help is much appreciated!

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JoeCab

· #2 · Jan 3, 2008

hmacris said:
How should the rubber guibos be in relation to the driveshaft? I think it may be coming from the middle guibo... !

The flex discs cannot be oriented incorrectly, so that is not likely your problem. Driveshaft balance is an issue on these cars, and can be very difficult to correct once it gets out.

There are a couple of things that can happen:

1) The driveshaft halves can be re-assembled in a different orientation than they originally were. Usually one would mark them so this doesn't happen. Also, there are specific numbers of washers and nuts on each bolt on the driveshaft - these may or may not contribute to the overall balance, but it is a good idea to replace each set of washers/nuts in EXACTLY the same spot it came from.

2) If the car was driven for a long period of time after a flex disc "blew up", the yolks and splines can be damaged.

A good next move would be to remove the driveshaft and take it to be balanced. Not every driveline shop can balance a driveshaft that spins at engine speed, so ask around in your area and find a good one.

Joe

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Duk

· #3 · Jan 3, 2008 (Edited)

JoeCab said:
A good next move would be to remove the driveshaft and take it to be balanced. Not every driveline shop can balance a driveshaft that spins at engine speed, so ask around in your area and find a good one.

Joe

Joe, every rear wheel drive car has the tailshaft turn at or above engine speed when the car is in forth gear or higher. Front engine/rear transmissions cars have there tailshaft turn at engine speed all the time.

Check out Greg Gordon's sight for tailshaft and guibo info:
Guibo, DS, Clutch

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Alfissimo Int.

· #4 · Jan 3, 2008 (Edited)

hmacris said:
Hi All,

I am relatively new at this (20 years old). My family has had and driven Alfas for as long as I can remember. I recently bought an 88 Milano Verde that came with the evo front and rear bumpers. It vibrated horribly until I found out that one of the cylinders was not firing. This solved a lot of it, but there is still bad vibration in any rpms over 2000. I brought it to my local alfa guy who looked it over and said the driveshaft may have not been replaced correctly the last time the service was done and that it is most likely coming from that. How should the rubber guibos be in relation to the driveshaft? I think it may be coming from the middle guibo...

Any help is much appreciated!

Welcome.
I suggest reading Greg's article as well, it explains everything and should help you out. If that does not turn out to be the issue then maybe we can go through it more. One easy way to rule out some things is to rev up the engine in neutral and if you feel chassis vibration, then most likely it could be a balance issue/donut issue. Hopefully the balance tabs are still on the shaft. But I am going to say that it is one of the donuts that maybe bad or was not put on properly

Try driving it up to the RPM or Speed you feel the vibration and pull it out of gear, does it go away or stay?
If it is still there then there is a chassis/suspension/wheel issue.
If it goes away then it is a drive line issue

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JoeCab

· #5 · Jan 3, 2008

Duk said:
Joe, every rear wheel drive car has the tailshaft turn at or above engine speed when the car is in forth gear or higher.

Assuming 4th is direct and 5th+ are overdrive gears, then yes, that is true.

However, the balance issues on an Alfa transaxle car are much more important since the driveshaft is always at engine speed, so any periods of vibration are felt in all gears, not just 4th/5th.

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hmacris

Discussion Starter · #6 · Jan 3, 2008

I think it may be that the two halves were not re-installed correctly by the last person who did service to it. It will coast with little to no vibration, but even in neutral when the car is revved it vibrates which leads me to think its not the suspension or chassis.

There is a correct orientation of the first half to the second half of the driveshaft correct? I read an article saying to mark the donut with a marker or wax pen or something to ensure it goes back together so that it is oriented the same way. Is there a diagram showing correct vs incorrect orientation?

Is driveshaft removal relatively straight forward? Some say it is harder than others and that there are different ways it can be gone about...

thanks

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SamW

· #7 · Jan 3, 2008

It is not too bad, the best way to do it is pull the transaxle, but absent that, you need to at least drop the front end of the transaxle down to get the driveshaft to seperate from the transaxle, then unbolt the center support and take the pinchbolt out of the front connection. I would leave the rear donut/guibo bolted to the driveshaft, that way you don't have to worry about the rear bearing in the center of the donut. To split the two halves, you need to remove 3 of the 6 bolts and pull the two apart, if you plan on repositioning the two halves, the you will need to remove the center support and have either a 1 1/4" or (24mm I think) non-impact deepwell socket to remove the two jam nuts holding the center donut attachment to the front section. This should then slid off and you will see the splines which are similiar to the torsion bar splines, and this will allow you to re-position the two sections in smaller increments than the 6 bolts on the center donut.

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Duk

· #8 · Jan 3, 2008 (Edited)

JoeCab said:
Assuming 4th is direct and 5th+ are overdrive gears, then yes, that is true.

Which is 99.99% of front engine, rear drive cars.

JoeCab said:
However, the balance issues on an Alfa transaxle car are much more important since the driveshaft is always at engine speed, so any periods of vibration are felt in all gears, not just 4th/5th.

Sorry Joe, but I think these kind of statements are misleading to new (and sometimes older) Alfa owners.
Every front engined, rear drive car should have a well balanced tailshaft regardless of where the transmission is mounted and that, in my opinion (disclamer

), doesn't make the Alfa any more important than any other car. Tailshaft alignment, however, is very important in Alfa transaxle cars

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1166

· #9 · Jan 5, 2008 (Edited)

If you are still concerned about the 'balance' of your driveshaft, try looking at how the dounut installation was done. The center and rear sections have a low misalignment bearing that will snap overcenter and not properly center the driveshaft. If the installer was in a hurry, stupid, didn't care, whatever, it is pretty easy to mess it up. The front and rear sections must slide together easily, and the rear dounut must slide on - you cannot push them or you will probably overcenter the bearings.

While your at that, check the transaxle front mounts and make sure they are OK. If they are, check the distance of the 'pinion' snubber to clutch housing - it should be 1/8 to 3/16 of an inch. If the snubber is touching you will have a vibration. Measure the gap with a drill bit...

Suprisingly, you can install the dounuts incorrectly. I had a customer do it AFTER I told him he could easily do it himself if he marked everything and 'the dounuts only go on one way'. Well, he didn't pay attention to ANYTHING and he ruined 3 dounuts (every one installed wrong) and the center carrier in 50 miles! Thankfully I got it right the first time (he seperated the center yoke from the front and didn't mark it) and it was fine after that.

I believe that GENERALLY the driveshafts do not magically 'go out of balance', but that the ends 'bend' ( get tweaked ) when a dounut fails. The shaft will then rotate eccentrically and vibrate. I spoke to the guys at bennica alfa and was told they should be round to 1/2 thou of an inch(!!!) or they will vibrate. Most people have NO idea how great these cars are with a PERFECT driveshaft... Somewhere I made a list of 25+ things that can mess up the 'balance' of the driveshaft. Have fun and good luck!

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