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Discussion Starter · #1 · (Edited)
Hy,


I am experiancing an anoying shifter vibration at 130km/h up to 145km/h what is the speed you would normally drive at on motorway where I live. It only occurs in 5th gear. At same RPM in different gears no vibration is to be seen.

The shifter is slightly modified. The rod under the ball is extended 15mm for shorter throws and rubber bushing is replaced with a brass one. I think (but i'm not sure), the problem has been present before this mod.
The car is 1.6 Alfetta GT. Transmition is standard.


Is there a known problem with driveshafts vibration or something similar? Where should i look and how can I diagnose the problem better?


Thanks
 

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Check the drive shaft guibos / donuts / flex couplings. It could be that one is opening up at a fissure in the rubber and causing an imbalance at higher speed and load. Possibly the middle coupling nearest the gear lever, that would be the first place I would look
 

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Discussion Starter · #3 ·
Check the drive shaft guibos / donuts / flex couplings. It could be that one is opening up at a fissure in the rubber and causing an imbalance at higher speed and load. Possibly the middle coupling nearest the gear lever, that would be the first place I would look
Thanks,

All guibos are only 4.000 km old.... I will however re-check them.

Any other ideas?
 

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15mm you moved the pivot ball?
I'm gonna bet the long shifter rod from the shifter to transaxle is touching the body in 5th gear.
 
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Interesting issue. Does it go away above 145km/h? Basically is it behaving like a tire/wheel/brake imbalance?
Please report back about the possible interference mentioned by Slowcreek.
If there is no interference, try taping a weight on the selector shaft. Try it anyway.
 

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Rear wheel imbalance?
I think it absolutely can be this. It seems to me that when I deal with a tire shop (Costco, Discount tire, etc) about vibrations, they discount the fact that it can be a rear wheel. Which I find puzzling. I can only guess that old US domestics were softly sprung and underdamped from the factory.
How good are your shocks (dampeners)? Because on a stiffly sprung vehicle, non-steering wheel vibrations can be felt thru the body.
 

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Things to check:
Obviously, check guibos even though they are recently installed.
They may have been sitting in a warehouse for many years.
* Particularly the early style with aluminum inserts.

All guibo fasteners are equal in all instances.
All 6 nuts, bolts & washers are equal in the radial array through the guibos, in the front, in the center and in the rear.
When this arrangement spins, they have to have equal weight or the whole thing can vibrate.
The middle is most important.

Center support bearing rubber is good and fasteners are secure.

Nut & bolt through the shifter linkage that are beside the driveshaft are secure
and not hitting the driveshaft when it is under load.
Larger side away from the driveshaft.

Driveshaft was marked and reassembled correctly by you or your mechanic.

Centering pilot bearings are lubricated and seated correctly.

My experience has been that if you ONLY feel the vibration in the shifter, your driveshaft is probably okay.
Shifter only, my shifter linkage bolt was hitting the driveshaft.

I felt driveshaft vibration in the whole car when my pilot bearing was not seated correctly.
Another time when a guibo broke.
Limped home with that.

Many years of dealing with Alfetta driveshafts so I've learned a few things.
I hope this helps!
 

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Discussion Starter · #11 ·
Thank you all for sharing you experiance. you gave me quite a feu points to look at


I will take more time to check all during weekend.
and yes, the vibration goes away above 145 km/h
The dampers are 2 years old koni yellows, they seem to be good.

vibration can only be felt at this speed in 5th gear, I have not checked it in 4th.....
Only the shifter shakes, the chassis seems fine.


See the video bellow. I recorded it today driving to work in the morning:)
 

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Hy,


I am experiancing an anoying shifter vibration at 130km/h up to 145km/h what is the speed you would normally drive at on motorway where I live. It only occurs in 5th gear. At same RPM in different gears no vibration is to be seen.

The shifter is slightly modified. The rod under the ball is extended 15mm for shorter throws and rubber bushing is replaced with a brass one. I think (but i'm not sure), the problem has been present before this mod.
The car is 1.6 Alfetta GT. Transmition is standard.


Is there a known problem with driveshafts vibration or something similar? Where should i look and how can I diagnose the problem better?


Thanks
There’s a reason it’s rubber. If you hold the shifter does the vibration/ noise change?
 

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Yes, if I just touch it the noise stops.

AND, you say the shifter has had the modification to it? Where the ball is moved on the shaft to change the pivot point and thus shorten the throw? 15mm you say?
Generally, if the ball is moved more than 10mm, the rod running from the bottom of the shifter to the transaxle rubs on the underbody. This rubbing is the worst in 5th gear due to the geometry of the modified shifter.
It's time for you to do a visual inspection under the car.
 
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my 79 shifter rattled a lot. When I rebuilt the transaxle, I found the shift rod (main one that interfaces with the three selector forks) had a loose staked clamp where the spring that holds it tight had given way - thus the shift rod was loosey goosey (not held by the spring tension) and the rattle carried up to the shifter rod in the car (solid linkage). There was no precision on gearshift position as the rod was fairly free to 'float' back and forth mostly, but a small bit fore and aft. I had to source a replacement for that shifter rod, and now, my 79 Alfie could easily be a gate-shifted Ferrari.
 
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Discussion Starter · #20 ·
my 79 shifter rattled a lot. When I rebuilt the transaxle, I found the shift rod (main one that interfaces with the three selector forks) had a loose staked clamp where the spring that holds it tight had given way - thus the shift rod was loosey goosey (not held by the spring tension) and the rattle carried up to the shifter rod in the car (solid linkage). There was no precision on gearshift position as the rod was fairly free to 'float' back and forth mostly, but a small bit fore and aft. I had to source a replacement for that shifter rod, and now, my 79 Alfie could easily be a gate-shifted Ferrari.
Thanks for that point.
Mine shifts beutifly and I am super happy about the shift feel....
I also made the connection between the vertikal and horizontal rods using needle bearings, so it is super notchy......


The vibration was already present before I replaced worn original bushing

I did not get to further investigation yet.... Having a new kid in the house takes quite some time away from my daily schedule :)
I will keep you poster after I get under the car ;)
 
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