Strong bumps in the cardan shaft

[Michaelz]

Hello to everyone.

I've started breaking in period on my Q4 transmission.

The problem is a few strong bumps in the area of cardan shaft (it's rear part mostly) when starting. Only when releasing the clutch softly.

What I did already:
1) Clutch checked - everything's ok, flywheel and cover are balanced and good. The clutch itself is new

2) I've cheked the first shaft suppot (closer to the distribution box) - no play, rubber is mint etc...


What I can see is old rubber in the second support (located on the solid part of the shaft, that's inside a pipe). There's some play (up and down) in it. Could it be the reason?

The play on the shaft itself is few degress (when rotating with hand), the slots on the shaft's end are good... Usually when the play on diff is too big - it should be on big bump, and I have few and only when softly releasing the clutch.



I'm still fear that is can be the rear diff itself, but want to eliminate other suspects before ripping the diff...


Thanks!
And sorry for my english.

[arjunior45]

Do you feel it only when "starting" with the 1st gear or every time you release the clutch slowly {for example passing to 2nd gear or 3rd gear or higher}?

[na15575]

i thing that you have the same problem like me
but first answer to arjunior45
and then we see if it is exactly the same

[Michaelz]

Do you feel it only when "starting" with the 1st gear or every time you release the clutch slowly {for example passing to 2nd gear or 3rd gear or higher}?

It's the same on changing gears also.

So when moving on 1st and then slowly changing to 2nd - I have the same bumps...

It really depends on releasing speed.

So I think when the clutch slips it causes the rear diff to move up and down, and a play somewhere causes the bumps...

[Michaelz]

i thing that you have the same problem like me
but first answer to arjunior45
and then we see if it is exactly the same

I can't wait to hear what your case was...

I'm really desparate to find the reason of this misterous bumps!

[Juan AR155Q4]

I think this has become an usually thing in Q4s...

Check this thread.

Edit: Also check this one too.

[Michaelz]

I think this has become an usually thing in Q4s...

Check this thread.

Edit: Also check this one too.

I've searched these treads...

Have few question left.

1) In my case I can feel not only the sound, but the vibration also (together with bumps)

2) I can feel it every time on changing gears, not only while taking off (mostly on 2nd and 3rd, almost none on higher gearx, because of less clutch slipping I think).


So now I will check:
1) The bolts that hold the last (piped) part of the shaft to the reductor (diff)
2) The rubber on this last part
3) CV joint.
4) Rubber between the subframe and rear reductor (diff)

Hope it will help!


Anyway, what was the case of NA15577? Please!

[na15575]

mine is make the same like yours but only when starting (taking off)
i believe that this is from my clutch
i suggest you to first check your clutch especially if he have some years on
the springs of the clutch can break easy
and make all this mess

[na15575]

what clutch you have use?

[Michaelz]

what clutch you have use?

I used stock clutch, kit from Alfa 164 Q4 (245mm), and now on Paddle kit.

So it's definitly not clutch in my case (


Will let you know about the progress tomorrow

[Michaelz]

So in my case there were two reasons:

1) Old rubber on the "piped shaft" supporter. I put a piece (1 cm thickness) of rubber between it and the bodysheel and tightened.

2) The mount of handbrake cable was too close to shaft, so when this piped part played, the bumps came from the mount.


I moved it away and yo-hooo! The bumps have gone!!!!
At least for now...

[na15575]

so you mean that the bumps comes from the hand brake mount ???

[Michaelz]

so you mean that the bumps comes from the hand brake mount ???

Well, the sound itself - yes. But vibration still appears in the area of this rear supporter. So I'll need poly rubber for tightening the pipe inside the mount.