Vibration at 60 and 120 Km/h (38 and 75mph)

[Danny Wilde]

Hi all! I wonder if anyone can be so kind of giving me some advice on this
I had a vibration problem at 60 and 120 Km/h so I replaced the following:

front axle: L&R thrust rods, L&R wishbones, L&R stabiliser links, center and L&R side steering rods, the steering idler arm
rear axle: L&R Pitman arms, L&R stabiliser links
Then I got the balancing and toe-in of the wheels done.

(earlier on I had already replaced both transmission rubber mountings (it's a manual), mounted Bilstein B4 shock absorbers, and replaced the differential gaskets).

However the vibration is still there , less evident, but still there… Does anyone have a clue of what is causing it?
I was wondering if the drive shaft center mount and/or the guibo rubber joint could be the cause… I thought I should warn you that I still haven't replaced those.

Thanks as always for you help ,
Danny

[Brucey]

some possibilities:

1) the tyres (and/or wheels) are not round

2) the wheel balance still isn't correct; (most likely because the flat spots were not run out of the tyres before they were balanced; my advice is to drive about 20 miles, then jack the car and remove the wheels inside five minutes.)

3) the brakes are dragging slightly

4) the wheels are not running concentric on the hubs. If you are using wheel spacers and/or hubcentric rings there are numerous different ways this can go wrong.

5) propshaft out of balance (eg failing/loose splined joint, failng centre bearing, failing damper, failing guibo, bad centring bush (at front end of propshaft)

6) bad diff mount

BTW a common cause of 3) is that the brake MC is failing.

cheers

[Danny Wilde]

wow Brucey thanks! that was a quick answer!

1) the tyres (and/or wheels) are not round
will get it checked

2) the wheel balance still isn't correct; (most likely because the flat spots were not run out of the tyres before they were balanced; my advice is to drive about 20 miles, then jack the car and remove the wheels inside five minutes.)
will get it checked

3) the brakes are dragging slightly
As a matter of fact the brake MC was the first thing I replaced after the purchase of the car 4 years ago, along with new disks, new brake hoses, new cylinders, and of course caliper refurbishment and new brake fluid and pads. Could the MC be failing already?

4) the wheels are not running concentric on the hubs. If you are using wheel spacers and/or hubcentric rings there are numerous different ways this can go wrong.
No spacers or rings are mounted but I'll get it checked too

5) propshaft out of balance (eg failing/loose splined joint, failng centre bearing, failing damper, failing guibo, bad centring bush (at front end of propshaft)
Now that you mention all these possible issues with the propshaft, I think it might be wise to let you listen to this strange sound I hear (sometimes) from BEHIND when releasing the clutch (clutch kit is new) and moving from a standstill in 1st gear, or at extremely low speed while releasing in 2nd, might be coming from the diff or the shaft(?) but not sure really, maybe it might be connected with this vibration issue at higher speeds? Here's a recording I've made, maybe it might give us some clue:

http://web.tiscali.it/webspace7/635_rum ... rtenza.mp3

6) bad diff mount
will get it checked

BTW a common cause of 3) is that the brake MC is failing.

cheers
thanks

[Brucey]

you would have to be incredibly unlucky if a 4-year old MC was going bad.

Regarding the roundness of tyres; I have found that a tyre can be perfectly round at 'balancer speeds' but have a hidden carcass fault which allows the tread to bulge outwards at higher speeds. It doesn't sound like that in your case; the symptoms of this are usually that there is a bad vibration at 80mph which gets worse the faster you go.

When the front wheels vibrate the typical mode is that the whole upright moves back and forth and the upper TCA bushing flexes. Obviously not all upper TCA bushings are equally stiff, and wheels are not all the same weight, so the exact speed of worst resonance will vary. But a typical 6er will shake its front worst at about 60mph and the half-speed resonance may not be apparent at all.

You can often tell it is a front end problem because in a long sweeping constant speed turn, the vibration will change through the steering as the front wheels (which are not going equal speeds) go in and out of phase with one another.

Iffy propshafts can do all kinds of weird things. In a hard launch there is potential for all kinds of flapping around and it doesn't take much wrong to cause problems. I'm most suspicious of your propshaft and its associated parts tbh.

cheers

[Danny Wilde]

Brucey thanks for such an in depth analysis, I will get all those areas checked
Sorry if I repeat myself , have you ever heard that strange sound coming from the rear?

http://web.tiscali.it/webspace7/635_rum ... rtenza.mp3

[Brucey]

Diagnosis from such noises is notoriously tricky, but not quite completely pointless trying I suppose.

The whining noise sounds to me like a noisy diff (or gearbox if it is further forwards) but it could also be a failing centre bearing. BTW if the rear subframe is making hard contact (i.e. not via rubber mountings) with anything it shouldn't, a diff that is just fine can sound terrible, because the noise is transmitted. Ditto if the centre bearing support is bad.

cheers

[Danny Wilde]

Well, as usual, you nailed it Brucey thanks!!!!!
Finally managed to replace the propshaft damper, guibo, centre bearing, centring bush and both swivel joints, the damper in particular was pretty shot, and both vibrations at 60 and 120 Km/h have disappeared!!!!!

but…

It now has a more noticeable vibration at 20 Km/h (more or less), but I think it's more related to rpm. If I start gently when in 1st gear I can barely feel it, but if I make a quicker start the vibration is pretty evident.

Could it be that they made some mistake while replacing parts on the propshaft? Has anyone had a similar vibration?
Thanks again,
Danny

[nick88highline]

It now has a more noticeable vibration at 20 Km/h (more or less), but I think it's more related to rpm. If I start gently when in 1st gear I can barely feel it, but if I make a quicker start the vibration is pretty evident.

Could it be that they made some mistake while replacing parts on the propshaft? Has anyone had a similar vibration?
Thanks again,
Danny

I replaced my propshaft with a new one (from BMW) a month ago and I've got vibration at the speeds you originally posted about! I'm wondering whether this is a more difficult task than the manuals make out...although I cannot see why.

It sounds like your 20mph vibration may be related to the centre bearing pre-load. When the propshaft is installed the centre bearing mount should be pushed forwards by about 4-6mm for these later cars. If it is not the shaft can wobble around at low speeds, particularly when accelerating, but I'm sure whoever installed the shaft knew that.

[Brucey]

FWIW it is possible (easy in fact...) to install the guibo the wrong way round. This can create all kinds of weird vibrations that are sensitive to the torque in the drivetrain too. Worth double checking this!

Also, apologies if this is obvious, but if the gearbox mountings are in bad shape, this can cause all kinds of trouble too. It is best to check these by holding the gearbox on an axle stand and then remove the crossmember and/or mounts. They quite often delaminate in a way that isn't noticeable unless you make a special effort to check them.

cheers

[Danny Wilde]

FWIW it is possible (easy in fact...) to install the guibo the wrong way round. This can create all kinds of weird vibrations that are sensitive to the torque in the drivetrain too. Worth double checking this!

Also, apologies if this is obvious, but if the gearbox mountings are in bad shape, this can cause all kinds of trouble too. It is best to check these by holding the gearbox on an axle stand and then remove the crossmember and/or mounts. They quite often delaminate in a way that isn't noticeable unless you make a special effort to check them.

cheers

1) Thanks Brucey , finally got a chance to take a few pics of the new guibo below, it actually looked quite similar on both sides to me, from what you can see from these pics do you think it's been mounted correctly? Should I be looking for some particular visible feature or writing?

I got the mech to go through the center bearing preloading process again just to make sure. He fixed the shaft in place and left the centre bearing loose and secured it for last after preloading it by 5mm towards the front, is that the correct procedure?

Unfortunately the vibration is still there , but I can now be more precise, it can be distinctively felt between 1500 and 2400 rpm in 1st and 2nd during a vigorous acceleration. In 3rd it is much less noticeable...

2) Brucey, no suggestion is never too obvious for me . But yes, I already put new original gearbox mountings 2 years ago, thanks…
Any more guesses?

I replaced my propshaft with a new one (from BMW) a month ago and I've got vibration at the speeds you originally posted about! I'm wondering whether this is a more difficult task than the manuals make out...although I cannot see why.

It sounds like your 20mph vibration may be related to the centre bearing pre-load. When the propshaft is installed the centre bearing mount should be pushed forwards by about 4-6mm for these later cars. If it is not the shaft can wobble around at low speeds, particularly when accelerating, but I'm sure whoever installed the shaft knew that.

Dear nick88highline, thanks for your kind support , I got the mech to re-check that the centre bearing had a 5mm preload towards the front, unfortunately no luck, the vibration is still there.
Concerning your problem, I can tell you that in my case the cause was almost 100% due to a totally shot propshaft damper, the one that sits around the guibo, my one had nearly all of the rubber gone, of course I also changed all the rest (except for the propshaft itself) that is damper, guibo, centre bearing, centring bush and both swivel joints, but the damper was the one in the worst condition. After that the vibrations at 60 and 120 have completely disappeared!
I guess you already changed your damper?

Thanks for your help guys
Danny

[nick88highline]

So your problems are all fixed now? It was the propshaft damper?
Mine is an auto so it has no propshaft damper, but thanks for the suggestion.
Nick

[Danny Wilde]

So your problems are all fixed now? It was the propshaft damper?
Mine is an auto so it has no propshaft damper, but thanks for the suggestion.
Nick

The shot damper was the cause of the vibrations at 120 and 60Km/h, but I still got this pretty obvious vibration at low speed between 1500 and 2400 rmp in 1st and 2nd which I can't figure out unfortunately...

Hope you'll find the cause of yours Nick!

[Danny Wilde]

Dear Brucey, sorry to bump ... but I really can't figure out this vibration between 1500 and 2400 rpm , everything's new in the propshaft… when you have a minute can you take a look at the pics above and see if the guibo, as suggested by you, has been mounted the right way round?
thanks a million
D

[nick88highline]

So your problems are all fixed now? It was the propshaft damper?
Mine is an auto so it has no propshaft damper, but thanks for the suggestion.
Nick

The shot damper was the cause of the vibrations at 120 and 60Km/h, but I still got this pretty obvious vibration at low speed between 1500 and 2400 rmp in 1st and 2nd which I can't figure out unfortunately...

Hope you'll find the cause of yours Nick!

I did find mine and it was the centre bearing. Basically if I removed the pre-load, the vibration went away. Not saying this would work for you, but it might be worth loosening the centre bearing and let it find its own position, then re-tighten and see what happens. This goes against everything (well, more or less) that you will be told and have read anywhere and everywhere.

[hornhospital]

Danny, the arrows on the flex disc/giubo/guibo (take your pick) are supposed to point toward the flanges. You've got the disc aligned wrong. Unbolt and rotate 60°, then reattach.

[Brucey]

Danny, the arrows on the flex disc/giubo/guibo (take your pick) are supposed to point toward the flanges. You've got the disc aligned wrong. Unbolt and rotate 60°, then reattach.

FWIW I agree, that does appear to be the case.

cheers

[Danny Wilde]

thanks for your support!!
Well… this is quite embarrassing , we partially unbolted the flex disk to check and it looks like it's been mounted correctly all the time, he must have corrected it's position AFTER I took the earlier pics above…. sorry guys!

Needles to say of course that the vibration issue must be caused by something else… but what?
Here are the some more recent pics of the flex disk below, the arrows are in fact pointing towards the flange "fingers" as required. I gather my flex disk is the kind that can be installed on either side right? I also posted pics of the rear end of the shaft, just in case some of you spot something wrong over there...

1) The mech suggests getting the prop shaft rebored and rebalanced (pretty expensive), but the prop itself is still the original one and had no issues before replacing all the other parts. He's also positive he reinstalled the prop the right way because he said there is just one way to reinstall it correctly.

2) Could it be the new Meyle swivel joints? I mostly get original BMW parts but this time I got them on ebay, found them searching via the OEM n° 26117518304, the Ebay vehicle compatibility test said "not compatible" but the oem N° is correct, and the list includes practically all E24 models except my 1986 manual 635 ?!? There had to be a mistake I thought, and bought them all the same, what do you think?
http://www.ebay.co.uk/itm/142249035006? ... EBIDX%3AIT

Must admit I'm really out of clues now
thanks as always guys
Danny

[Brucey]

my understanding is that if you replace the swivel cruciforms etc it is pretty much mandatory to rebalance the propshaft. If you have not done that, I'd suggest that you do so. The reason is that there may be a tiny offset in the positions of the parts once they are replaced.

BTW it certainly is possible to fit the propshaft wrongly; the splined joint can be reassembled in the wrong orientation for example.

cheers

[Danny Wilde]

my understanding is that if you replace the swivel cruciforms etc it is pretty much mandatory to rebalance the propshaft. If you have not done that, I'd suggest that you do so. The reason is that there may be a tiny offset in the positions of the parts once they are replaced.

BTW it certainly is possible to fit the propshaft wrongly; the splined joint can be reassembled in the wrong orientation for example.

cheers

Finally got the propshaft rebalanced by a specialised shop, and they got the 2 swivel cruciforms replaced again in the process.
Must say that the rebalancing has definitely improved the situation Brucey thanks!
I would say that the vibration has decreased by 50%, so I guess that the slightly out of balance shaft was certainly contributing to the vibration, but I must admit I'm still curious to get to the bottom of this, at this stage, as you suggested Brucey, could it be that my mech connected the spline joint offset?
Since he probably had not made any mark before removing, is there a way to check which is the correct alignment now?
thanks again!
Danny

[Brucey]

the U joints should align in a specific way between the front and the rear sections of the propshaft. IIRC there is an even number of splines so in theory there are two 'basically correct' positions for the splined joint. However;

- if the prop has been balanced in one orientation, it won't be balanced in any other and
- if the spline joint is extended or compressed dramatically from the position that it was balanced in, it may no longer be in balance
- I have seen some propshafts that will always contain a small alignment error; none of the spline orientations correspond with perfect front to rear U-joint alignment.

Note also that the diff input shaft needs to be perfectly parallel to the gearbox output; this can be checked using a digital tilt meter. If there is an error (eg due to failing/bad engine, gearbox or rear subframe mounts), the result will be 'quarrelling vibrations' that cannot be entirely eliminated.

As per another thread, there are such things as 'bad propshafts' and sometimes these come from the factory. It may be that the perfect balance in the propshaft may only be achieved if the shaft is articulated in the same way as when it is installed in the vehicle; this is something to discuss with the people who do the balancing for you.

cheers

[Danny Wilde]

the U joints should align in a specific way between the front and the rear sections of the propshaft. IIRC there is an even number of splines so in theory there are two 'basically correct' positions for the splined joint. However;

- if the prop has been balanced in one orientation, it won't be balanced in any other and
- if the spline joint is extended or compressed dramatically from the position that it was balanced in, it may no longer be in balance
- I have seen some propshafts that will always contain a small alignment error; none of the spline orientations correspond with perfect front to rear U-joint alignment.

Note also that the diff input shaft needs to be perfectly parallel to the gearbox output; this can be checked using a digital tilt meter. If there is an error (eg due to failing/bad engine, gearbox or rear subframe mounts), the result will be 'quarrelling vibrations' that cannot be entirely eliminated.

As per another thread, there are such things as 'bad propshafts' and sometimes these come from the factory. It may be that the perfect balance in the propshaft may only be achieved if the shaft is articulated in the same way as when it is installed in the vehicle; this is something to discuss with the people who do the balancing for you.

cheers

Brucey, thanks for taking the time to provide such precious info , I will elaborate all this with my mech and will report the results…
best
Danny

[Danny Wilde]

Diagnosis from such noises is notoriously tricky, but not quite completely pointless trying I suppose.

The whining noise sounds to me like a noisy diff (or gearbox if it is further forwards) but it could also be a failing centre bearing. BTW if the rear subframe is making hard contact (i.e. not via rubber mountings) with anything it shouldn't, a diff that is just fine can sound terrible, because the noise is transmitted. Ditto if the centre bearing support is bad.

cheers

Dear Brucey, I've replaced the whole clutch kit and this part of the issue, the mysterious noise, has disappeared!
If anyone of you guys ever hear this sound you can be sure it's a faulty clutch kit:

http://web.tiscali.it/webspace7/635_rum ... rtenza.mp3

Looks like the previous kit (only 2 years old actually) was not making full contact on the plate and due to it not fully engaging it produced that sound I guess..
Thanks again guys
Danny