Drive Shaft Noise - Intermediate Bearing?

[rg]

Norrie,

Thanks for your wise and helpful response!

I was a little too cautious to try your stethoscope approach, as I lack a reliable assistant, and space on the drive is limited. I've had an incident with a runaway Seicento in recent times, so proceed with much caution.

There was much wear in the intermediate bearing, and I really did think that I'd found the problem. There's no sign of anything else rubbing, and the noise changes per application of lock, so the wheel bearing is the only likely source, unless it's something weird in a driveshaft, but I'm sure that it would be more "clacky/clunky" - this is certainly a "consistent rotary" noise.

The disks were changed around ten years ago, and "the boy" at my independent did indeed attack them with a hammer. There was always a very slight high-pitched noise on right lock, but the bearing lasted over 100K before replacement.

There's no distinct smell of brakes binding.

I can only conclude the following:-

1/- The bearing was pressed in incorrectly, with pressure on the inner race, causing damage.

2/- Inferior materials have been used in manufacture. This was bought from AEP in Glasgow. I don't think I'll have any chance of free replacement, as they will question the possibility of point "1" above. Unless they've had a batch of bad ones...

Apparently, the heavier models of CX used to eat bearings. However, my damaged one did 166K, and the left side is original at 187K.

It looks like time for a new bearing. At least I'm familiar with the dismantling sequence now...

Thanks, once again, for taking the time to reply.

Rob

[rg]

Drat!

I've now changed both wheel and intermediate bearing in recent weeks, and the noise persists!

It's classic wheel bearing noise, but it isn't the wheel bearing. The drive-shaft does not "clack" on any lock. The noise changes with application of lock, just like a wheel bearing. And it sounds like a bearing in it's "drumming", with a particularly loud period between 40 and 55.

It can now only be two things:-

1/- The caliper which is loose on the pin and "hunting" on it (although the noise persists when I gently apply the parking brake on the move)

2/ - Something weird with the drive shaft CV joint(s).

Norrie, I think I may have to employ your "spin up on one wheel" technique to rule out "1".

It's been lots of work for very little return so far, so all suggestions welcomed!

r

[noz]

Hi Rob,

I think you've almost eliminated everything else leaving the only real viable culprit as the CV joint. The CV joint noise would change as you turn the steering wheel whilst driving the respective wheel whether on the road or on the jack. Unfortunately, since it rotates, there's no way to touch it with a stethescope. You can only listen to the hub next to the CV joint and try to determine if the noise is being transmitted from the CV joint through the hub.

In an ideal world you would run the wheel at a constant speed and take vibration readings with a vibration sensor. By knowing the number of balls in the bearing and the (fewer) number of balls in the CV joint you would be able to see sub-harmonics on the resultant graph. e.g. if the bearing had, say, 12 balls then you would see the fundamental frequency at the wheel rotation rate and then a further set of sub-harmonic peaks at 1/12 of the fundamental or 12x the fundamental depending on how you want to look at it. If however, the peaks are at 1/6 or 6x fundamental and there are 6 balls in the CV joint then it points to a failure of the CV joint.


Just as an aside, you must have disconnected the stub shafts when doing the wheel bearing. This would have entailed removing the large 35mm AF nut from the centre of the wheel(which would have been tight). The reason for the tightness is that the pre-load on the bearing is achieved by tightening this nut until the two halves of the inner bearing race touch in the middle. I can't remember off-hand how much torque is required but its a lot. Once they touch, the correct amount of pre-load has been applied. Of course, the mating faces of the two halves would need to be clean otherwise any grit or dirt between the faces would keep them apart. Without the required amount of pre-load the bearing will not perform well and is likely to be noisy. Can I respectfully ask how this was achieved when the bearing(s) were replaced? Were the two mating faces of the inner races clean on assembly? Was the right amount of torque applied when tightening the hub nut? At this stage, I'm grasping at straws so please forgive the somewhat basic nature of the questions.

cheers

noz

[rg]

Hello Noz.,

Many thanks, as ever.

Re the bearing pre-load - this was beyond the range of my torque wrenches, so was torqued to the limit of one of them, then given 1/16th of a turn with a breaker bar and scaffold tube (!), so should be adequate, although this may be an area to revisit.

The drive shaft was plonked on the counter of my independent Citroen chap, and I demonstrated the end-float of the outer joint, asking his opinion. He seemed to think that this was OK. Rotational play was minimal.

One observation which might be pertinent is that, when I removed the wheel bearing nut to remove the shaft, this was quite easy to remove, although it had been torqued up in the manner described below. I'm not sure how this might be so, as it does not bear againstanything that wears, so I understand. The nut lockign device was intact.

I'm struggling to find anywhere via on-line search that re manufactures drive shafts. Does no-one do this these days?

Next stop will probably be the caliper, as this will start causing other problems soon, and needs to be changed. Once that is done, the only thing left will be the drive shaft.

Thanks, once again!

Rob

[nightmare]

Did you ever get this fixed?
If so What was it?