What is this sound?

[muld]

Recently i've noticed (mainly on de-acceleration) a very loud throaty (kinda diesel like) sound which seems to be coming from front passenger side (possibly central). The sound is only present when the car is moving but it doesnt seem to be linked to revs, it is however linked to speed. The faster i go the faster the sound. Have a listen, let me know what you think, i've poked about underneath and listend to the exhaust and i cant hear anything, nothing feels like it could be loose/rattling either. The noise lessens when not in gear or clutch is fully depressed and get louder again at biting point.

listen for the end of the vid as i de-accelerate still in gear. if i sit on the drive and rev it i can't hear the sound. Below is what it sounds like stationary.

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[aliengravy]

rubbing arches??? Wheel bearing?

 

[muld]

The wheels have been on for ages, no sign of rubbing, i did jack the wheels up earlier to see if there was any play but they are as tight as ever

 

[Henry]

speed related's going to be something to do with the tyre, wheel, brakes, hub/bearing, driveshaft, diff. doesn't help particularly - just gives you a list, in ascending order of expense/difficulty

 

[muld]

hehe, thanks, i've just had new pads all round and the disks are a little worn but seem ok, spinning the wheel when jacked up i can't hear anything that would be causing it from there. Oh forgot to mention, there did seem to be a fair amount of gearbox oil on the undertray when i removed it which looked quite fresh, is this worth checking? / replacing, car performs fine btw, no problem with gear changing or performance, i can hear a slight background whine on accelelaration above 40 or so (4k revs +) but that was always there i think ;o)

 

[Henry]

hope it's not the diff then. it does sound like a bearing and seems quite loud - and you're obv. closer the diff than the hub

i'd stick the front end up on stands and have someone else drive the wheels to see if it does it then - should allow you to judge where it's coming from

 

[muld]

Have been to two garrages now and it seems i need a new gearbox (do'h), diff is shot

 

[muld]

what i'm confused about though is why i have no symptoms (apart from the noise) the gearbox feels fine, power is fine etc ;( any thoughts?

 

[Henry]

bad news about the diagnosis - bring on the pain:dapprove:

it's probably a bearing that's suffered due to lack of lubrication - noise is often the first symptom and they can go on for quite a while before they seize/break up (if they ever do). same happened with mine - slight noise from the diff (only audible whilst spinning a wheel during service); i had a gear oil additive put in (which helped); gearbox seized about 10k later

depends what you want to do really. you could fix the leaks and put an additive in to see if that helps (sounds unlikely tbh - it's quite noisy), or you could pre-empt its potential failure and look into doing the gearbox now

 

[muld]

not a bad idea, its worth a go anyway, lol. it can't make it worse what additive did you use? What would happen if i ran it till it failed?

 

[Henry]

someone put an additive in it when i had the cambelt and a few other bits done, and i can't remember what it was that was used. could fire up another thread and ask for recommendations.

regarding what might happen if/when it goes - difficult to say really. mine seized (which can obviously be dangerous), but i guess they can let go in other ways - bearings breaking up, increasing difficulty in selecting gears cleanly, lever popping out of gear, etc. it's not just your diff that's going to have suffered - if it's been run low on oil, presumably all of the other friction bearing components will also have been affected in some way.

personally, if you can live with the noise, i'd spend a little on fixing the immediate problems (leaks) and run it until it pops. might go on forever; might go next week - no way of knowing what state everything's in without going to the expense of removing and stripping it.