Mysterious drivetrain rumble - how to find?

[Wookey]

I have a mysterious drivetrain rumble, and am wondering how I work out which bit it is.

1997 Expert TD van, 158000 miles, so getting a bit tired. Have owned since 2000 and not had any drivetrain trouble - just had to replace the gaiters in last few years. Or put another way everything is old. Oh yes, and it's the original NA gearbox with a 1994 Xantia TD engine (changed in 2003).

So, about 2000 miles ago, heading out to Austria for the summer, I noticed a wheel-bearing sort of rumble on the motorway. Bum, I thought, can't fix that for a while. I initially thought it was a wheel bearing, but there is no sign of a different noise when cornering in either direction. Noise is road-speed related, not engine-speed related. A rumbling noise rather than actual vibration. Same in and out of gear. Acceleration/deceleration doesn't obviously make a difference. Rolling down a hill just the same as driving along. So I think that mean bearings, driveshafts, and diff. Right? (maybe some other bits of gearbox?). Most likely wheel-bearings, intermediate driveshaft bearing, or differential/gearbox bearings?

Noise is much worse above about 30mph, and very noticeable above 50mph. This makes it tricky to find on the driveway at home.

I just tried jacking up the front and poking about. No play in wheels so wheel bearings does seem ruled out. No obvious play in driveshafts, (tiny bit of backlash - I assume that's normal?). There is a little bit of movement where the nearside driveshaft goes into the diff. Very slight but it does move. Is that a clue?

I tried running the car whilst listening underneath but all that gets you is a lot of engine noise and vibration.

Spinning left and right wheels/driveshafts whist out of gear doesn't show anything noticeable.

So, how do I work out where the noise is coming from?

There is a lot of backlash in the diff between wheels. Is that normal (I think it is)?

Suggestions welcome. It sounds like the the sort of thing that will take quite a long time before it actually breaks, but I've used up 2000 miles already...

I guess I could try driving somewhere till everything is warm, then feeling for heat in bearings?

[white exec]

As you say, does sound like a wheel bearing. These can go noisy, even if they don't show any backlash/wobble. The roller bearing track (or the rollers) can develop flats, which produces the noise.

You might be able to detect which side it is by lifting the wheels off the ground, allowing wheels to turn under power (in gear, maybe a higher one, engine at idle speed), and using a listening stick on the back of each hub. If needs be, remove the wheel, and listen to each hub from the front side. Take all the usual jacking and support care.

If it is a wheel bearing, probably best to replace both sides.

[furriegurrie]

Could also be tires. Cupping or maybe a break in the steel belts in the tire

[Wookey]

Finally got round to taking the (nearside) hub carrier off. Bearing feels entirely smooth (surprisingly stiff, but then the replacement one doesn't seem much less stiff (maybe a tiny bit?)). So I guess that means my bearing is probably OK? Anything else I should test (beyond just turning slowly by hand) whilst I've got it in bits?
If I don't mind changing the gearbox oil I suppose I could take the driveshaft out and see if I can feel any dodginess there.
Would you recommend changing the bearing anyway as I have one, having got this far? It's much easier to just put it back together, but I can use the press at my friendly local garage - as I know this can be a big pain without a press. If I swap it and it's still noisy then I guess that's eliminated one part. On the other hand why replace perfectly good bits that are apparently still working fine?
Still, it's been rumbling for at least 5000 miles now and doesn't seem to be getting worse - maybe I should just put up with it a bit longer and wait for something to actually break
Suggestions from the committee welcome.

[civvie]

A few years back I took the wife's car in for its MOT, while he was checking the wheels the tester said the rear wheel bearing is on its way out. He spun the wheel slowly and we could feel roughness in the movement, he passed with an advisory. Purchased the bearing (for both sides) and forced the old one out. Next problem putting the new on in without damaging it as I didn't have a press. I put the bearing in the freezer over night, put the carrier in the hot oven for a few hours. Took them both outside and the bearing then just slipped in. Sorted. Good luck in finding it.

[Peter.N.]

The most likely cause is a worn wheel bearing, but generally they will only do it with the weight of the car on them. Have you tried the rear bearings, sometimes sound travels. It could also be a faulty tyre as mentioned.

Peter

[GoceKU]

Do you have a tick noise when rocking the vehicle in gear with the engine off. 1,9d that is a BE3 gearbox, i've dealt a lot with them, if you have access to an inspection pit grab both axles and try rocking the differential to see do you have end play, you may need to add shims to take the space on the worn out bearing, easy to do on those gearboxes, even changing the diff bearings can be done easily in the vehicle.

[Wookey]

By 'rocking the differential' do you mean pull and push driveshafts (i.e one one way, one the other) perpendicular to the shafts? or pull/push both in same direction (still perpendicular to shafts). Or something else?
I tried rocking both opposite and together and just found that, at least with the intermediate bearing in, there is no movement whatsoever (although brake pipes in the way make it hard to get a really good shove)

[Wookey]

Just taken the driver's side hub carrier off too. Again bearing seems to be fine. I guess this fits with no difference on corners: maybe it's the rear. I see the rear bearings cost 4 times as much because they are integral with the hub.

[Peter.N.]

A second hand hub would be the way to go there, not only cheaper but easier than fitting a bearing.

Peter

[Gibbo2286]

Are the wheels tight? I had a guy complaining about 'wheel bearings' but all that was wrong was the wheels hadn't been properly torqued up.

[Xantic]

I have the same sort of thing on my 407 but on the rear, Jacked it up today but no problem i could find, I have pin pointed it to the nearside though as going around a left hand bend the noise goes.