G/box: 5 speed M47: - Unidetified Noise

Angie · Aug 26th, 2015, 22:35

Lately I've noticed a light grating sort of sound, very quiet but quite distinct, when moving slowly. It seems to be coming from the gearbox, it's there when coasting in neutral and when moving slowly in first gear. It's not disturbing yet, but has become a little louder over time, and on a 'stitch in time' principle I thought it ought to be seen to sooner rather than later.

Could it be gearbox or is it possibly the prop-shaft? I really don't know much about the transmission so any advice would be appreciated. I have very sharp hearing but I doubt the mechanic would hear much if I ask him to listen to it. Mechanics always seem to suffer a degree of hearing loss.

Clifford Pope · Aug 27th, 2015, 08:05

I think the first thing is to jack up the back wheels securely and lie under the car and rotate the prop shaft and see whether you can reproduce the noise.
Check the gearbox support mounting as well.

A likely candidate is the central support bearing in the rubber doughnut. Undo the two bolts holding its support member to release the doughnut, slide it clear of the bearing, and spin the bearing to see if it grates, whirrs or is stiff.
While the prop is loose, check for any stiffness in the universal joints. Refit and try waggling each joint in each direction to check for play.

Derek UK · Aug 27th, 2015, 13:21

Have you checked if there is anything rubbing/scraping in the brakes? Disintegrating handbrake shoes for example.

Angie · Aug 27th, 2015, 16:18

Thank you, Clifford, definitely a garage job, better get them to put it on the ramp and investigate. It sounds closer to the gearbox but I've learnt over the years that noises in cars rarely originate where they seem to, and it definitely relates to the motion of the car, in or out of gear.

Thanks, Derek, but I don't think it's brakes, it's a very regular and consistent sound. Another thing for the garage to look at though, and I want them to check brake pads soon anyway.

Angie · Aug 27th, 2015, 23:52

Are these bearings if that's what the problem is, likely to fail suddenly, or deteriorate quickly? The garage can't book it in until Wednesday and I have quite a bit of driving to do in the meantime. I wouldn't like to think that I'm risking causing further damage. It's fair to say that I first noticed the sound, and it was very quiet at the time, probably a couple of months ago, and it's taken that time, maybe 1,500 to 2,000 miles, to get to the point where I'm getting anxious about it.

Clifford Pope · Aug 28th, 2015, 09:20

No, unless it's getting suddenly worse.
The prop shaft bearing can go on for years making funny noises, and usually all it needs is a drop of oil injected behind the fibre seal of the ball race.

The M5 gearbox is not the most robust of the range, and does develop whine and whirring over the years. If the noise is actually from inside the box it would be worth changing the oil and keping the level well up - tilt the car when filling.

Angie · Aug 28th, 2015, 12:17

Thanks, Clifford, that's reassuring. It's a Torslanda, so a very late model, 1992, I'm not sure what gearbox that would have. I did wonder about gearbox oil, it hasn't been checked for quite a while so I'll get garage to change it anyway. I'll ask them to try putting oil in the bearing as well, to see if that improves things. They're very cooperative, and don't mind my relaying information I've received here!

coffeejunky · Aug 28th, 2015, 12:58

Quote:

Originally Posted by Angie

Thanks, Clifford, that's reassuring. It's a Torslanda, so a very late model, 1992, I'm not sure what gearbox that would have. I did wonder about gearbox oil, it hasn't been checked for quite a while so I'll get garage to change it anyway. I'll ask them to try putting oil in the bearing as well, to see if that improves things. They're very cooperative, and don't mind my relaying information I've received here!

I'd recommend asking them to use Volvo gearbox oil or if that is not possible, make sure they know the right spec of quality oil for the gearbox.
Although unlikely (as your car is immaculately looked after and it sounds like you have a good reliable garage on your hands), the garage may well assume you are in 'old banger' territory and put in the cheapest they have.
Not just a warning for you, but anyone else who may stumble across this thread

Aug 26th, 2015, 22:35	#1
Angie Premier Member Last Online: Jun 12th, 2024 22:53 Join Date: Apr 2011 Location: Lostwithiel	Unidetified Noise Lately I've noticed a light grating sort of sound, very quiet but quite distinct, when moving slowly. It seems to be coming from the gearbox, it's there when coasting in neutral and when moving slowly in first gear. It's not disturbing yet, but has become a little louder over time, and on a 'stitch in time' principle I thought it ought to be seen to sooner rather than later. Could it be gearbox or is it possibly the prop-shaft? I really don't know much about the transmission so any advice would be appreciated. I have very sharp hearing but I doubt the mechanic would hear much if I ask him to listen to it. Mechanics always seem to suffer a degree of hearing loss.

Aug 27th, 2015, 08:05	#2
Clifford Pope Not an expert but ... Last Online: Today 09:36 Join Date: Dec 2001 Location: Boncath	I think the first thing is to jack up the back wheels securely and lie under the car and rotate the prop shaft and see whether you can reproduce the noise. Check the gearbox support mounting as well. A likely candidate is the central support bearing in the rubber doughnut. Undo the two bolts holding its support member to release the doughnut, slide it clear of the bearing, and spin the bearing to see if it grates, whirrs or is stiff. While the prop is loose, check for any stiffness in the universal joints. Refit and try waggling each joint in each direction to check for play.

Aug 27th, 2015, 13:21	#3
Derek UK VOC Member Last Online: Jun 15th, 2024 11:39 Join Date: Jul 2006 Location: Chatham	Have you checked if there is anything rubbing/scraping in the brakes? Disintegrating handbrake shoes for example.

Aug 27th, 2015, 16:18	#4
Angie Premier Member Last Online: Jun 12th, 2024 22:53 Join Date: Apr 2011 Location: Lostwithiel	Thank you, Clifford, definitely a garage job, better get them to put it on the ramp and investigate. It sounds closer to the gearbox but I've learnt over the years that noises in cars rarely originate where they seem to, and it definitely relates to the motion of the car, in or out of gear. Thanks, Derek, but I don't think it's brakes, it's a very regular and consistent sound. Another thing for the garage to look at though, and I want them to check brake pads soon anyway.

Aug 27th, 2015, 23:52	#5
Angie Premier Member Last Online: Jun 12th, 2024 22:53 Join Date: Apr 2011 Location: Lostwithiel	Are these bearings if that's what the problem is, likely to fail suddenly, or deteriorate quickly? The garage can't book it in until Wednesday and I have quite a bit of driving to do in the meantime. I wouldn't like to think that I'm risking causing further damage. It's fair to say that I first noticed the sound, and it was very quiet at the time, probably a couple of months ago, and it's taken that time, maybe 1,500 to 2,000 miles, to get to the point where I'm getting anxious about it.

Aug 28th, 2015, 09:20	#6
Clifford Pope Not an expert but ... Last Online: Today 09:36 Join Date: Dec 2001 Location: Boncath	No, unless it's getting suddenly worse. The prop shaft bearing can go on for years making funny noises, and usually all it needs is a drop of oil injected behind the fibre seal of the ball race. The M5 gearbox is not the most robust of the range, and does develop whine and whirring over the years. If the noise is actually from inside the box it would be worth changing the oil and keping the level well up - tilt the car when filling.

Aug 28th, 2015, 12:17	#7
Angie Premier Member Last Online: Jun 12th, 2024 22:53 Join Date: Apr 2011 Location: Lostwithiel	Thanks, Clifford, that's reassuring. It's a Torslanda, so a very late model, 1992, I'm not sure what gearbox that would have. I did wonder about gearbox oil, it hasn't been checked for quite a while so I'll get garage to change it anyway. I'll ask them to try putting oil in the bearing as well, to see if that improves things. They're very cooperative, and don't mind my relaying information I've received here!

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