Drone and vibration from 996 rear axle - help!
11-20-2016, 05:32 PM
#1
Drone and vibration from 996 rear axle - help!
Hello everybody,
I own a 2002 996 Carrera (3.6, C2, coupe, manual, etc).
I love the car, but I'm having an issue with it and just wondered if the symptoms rang any bells for any of you...
As the title to the post suggests, there's a droning noise and slight vibration that feels as though it's coming from the rear of the car.
When I bought the car it had some old, worn-out tyres on it, and so expert opinion was that these would be the culprit. There is also minor impact damage on the inside of one of the rear rims (apparently).
However, I've since had the wheels checked over and restored, and fresh tyres fitted, and it's no better. The damage is very slight to that wheel, according to various people, and nothing that shouldn't balance out.
The noise is very surface dependent: it can almost fade to nothing, but is at its worst at a constant higher speed - e.g. 50-70mph - and on coarse road surfaces. It can get so bad that you'd have to shout even to be heard. I've driven 996s before owning mine and know they don't do this (despite being susceptible to having some road noise on our poor roads). The vibration is always there - it's slight, but it just feels like the car is permanently struggling with something. All in, it just makes me not want to drive it, so I'm very keen to sort it out.
The car has done 80,000 miles and I know it could do with a full suspension re-fresh. Would just like to sort this out now though if possible before saving up and then spending the big money down the line...
Any ideas?
Thanks in advance.
I own a 2002 996 Carrera (3.6, C2, coupe, manual, etc).
I love the car, but I'm having an issue with it and just wondered if the symptoms rang any bells for any of you...
As the title to the post suggests, there's a droning noise and slight vibration that feels as though it's coming from the rear of the car.
When I bought the car it had some old, worn-out tyres on it, and so expert opinion was that these would be the culprit. There is also minor impact damage on the inside of one of the rear rims (apparently).
However, I've since had the wheels checked over and restored, and fresh tyres fitted, and it's no better. The damage is very slight to that wheel, according to various people, and nothing that shouldn't balance out.
The noise is very surface dependent: it can almost fade to nothing, but is at its worst at a constant higher speed - e.g. 50-70mph - and on coarse road surfaces. It can get so bad that you'd have to shout even to be heard. I've driven 996s before owning mine and know they don't do this (despite being susceptible to having some road noise on our poor roads). The vibration is always there - it's slight, but it just feels like the car is permanently struggling with something. All in, it just makes me not want to drive it, so I'm very keen to sort it out.
The car has done 80,000 miles and I know it could do with a full suspension re-fresh. Would just like to sort this out now though if possible before saving up and then spending the big money down the line...
Any ideas?
Thanks in advance.
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stam+ (07-20-2023)
11-20-2016, 06:02 PM
#2
Pro
When you got the tyres balanced do you get them Road Forced? This helped mine a little and is a cheap next step.
Its also feasible that the wheel bearing or CV joints could be the source.
http://www.pelicanparts.com/techarti..._CV_Joints.htm
For vibration I would suggest it needs to be a rotating part.
Its also feasible that the wheel bearing or CV joints could be the source.
http://www.pelicanparts.com/techarti..._CV_Joints.htm
For vibration I would suggest it needs to be a rotating part.
11-20-2016, 07:31 PM
#3
Addict
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Lifetime Rennlist
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Four wheel alignment.
11-20-2016, 08:00 PM
#4
Burning Brakes
Does the noise change when accelerating vs constant speed vs decelerating?
Does the noise change when the clutch is pushed in vs out?
Does the noise change when going around a sweeping turn one way or the other?
You say the noise changes with the road surface... which leads me to think it's tires but let's rule out some other things while we're at it.
And yes, as said above... get an alignment.
Does the noise change when the clutch is pushed in vs out?
Does the noise change when going around a sweeping turn one way or the other?
You say the noise changes with the road surface... which leads me to think it's tires but let's rule out some other things while we're at it.
And yes, as said above... get an alignment.
11-20-2016, 08:37 PM
#5
Sounds like a bearing. If it goes away when the clutch is pushed it, could be in the gearbox. If not, a wheel. A bad wheel bearing will have some play when muscled around on jackstands.
11-21-2016, 05:28 AM
#6
Thanks for the replies everyone... 
My next step is to get it looked at more closely by a specialist. It's already been to one place but they couldn't see anything wrong...
I'd been putting off the alignment until I fitted the new suspension, but I fear it's looking as though it just needs to be all ripped off the car and started from scratch doing it properly... For a start there's a creak from the front axle over large bumps. The tech that drove also commented it 'understeered a lot' so perhaps it's way out of alignment too...
There's no noise when the clutch is in - it's only with road speed. Gets worse the faster you go, but doesn't seem to vary with turning the 'wheel either way. The vibration seems to get worse sometimes when you do turn the 'wheel, having said that.
My next step is to get it looked at more closely by a specialist. It's already been to one place but they couldn't see anything wrong...
I'd been putting off the alignment until I fitted the new suspension, but I fear it's looking as though it just needs to be all ripped off the car and started from scratch doing it properly... For a start there's a creak from the front axle over large bumps. The tech that drove also commented it 'understeered a lot' so perhaps it's way out of alignment too...
There's no noise when the clutch is in - it's only with road speed. Gets worse the faster you go, but doesn't seem to vary with turning the 'wheel either way. The vibration seems to get worse sometimes when you do turn the 'wheel, having said that.
11-21-2016, 05:31 AM
#7
Does the noise change when accelerating vs constant speed vs decelerating?
Does the noise change when the clutch is pushed in vs out?
Does the noise change when going around a sweeping turn one way or the other?
You say the noise changes with the road surface... which leads me to think it's tires but let's rule out some other things while we're at it.
And yes, as said above... get an alignment.
Does the noise change when the clutch is pushed in vs out?
Does the noise change when going around a sweeping turn one way or the other?
You say the noise changes with the road surface... which leads me to think it's tires but let's rule out some other things while we're at it.
And yes, as said above... get an alignment.
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11-21-2016, 12:56 PM
#8
Race Director
"There's no noise when the clutch is in"
This is the smoking gun. If all symptoms disappear when the clutch is depressed, the problem lives in the gearbox or engine.
This is the smoking gun. If all symptoms disappear when the clutch is depressed, the problem lives in the gearbox or engine.
11-21-2016, 12:59 PM
#9
Sorry, I think that's my mistake there and I replied too quickly. What I meant to say is that having the clutch in or out - when rolling - makes no difference to whether the noise is there or not. And there's no noise at all when at a standstill. Apologies again.
11-21-2016, 01:54 PM
#11
I'd been putting off the alignment until I fitted the new suspension, but I fear it's looking as though it just needs to be all ripped off the car and started from scratch doing it properly... For a start there's a creak from the front axle over large bumps. The tech that drove also commented it 'understeered a lot' so perhaps it's way out of alignment too...
11-21-2016, 05:55 PM
#12
No, the suspension currently on the car is standard spec (not MO30) and as far as I'm aware 14 years/80,000 miles old...
11-21-2016, 06:25 PM
#13
Race Director
* droning noise and slight vibration...coming from the rear of the car
* wheels checked over and restored, and fresh tyres fitted
* its worst at a constant higher speed
* creak from the front axle over large bumps
* tech that drove also commented it 'understeered a lot'
* No change in noise with speed change
First, the clunking/creaking from the front suspension is probably unrelated.
With the car in the air, in neutral, have you spun both rear wheels by hand? If a bearing is shot, you will likely feel a bump or grinding from the affected ball(s). As Ditto suggested, grabbing each rear tire (wear gloves) and trying to wiggle it from side to side can reveal bearing play.
Worrying about why the front end sometimes clunks or creaks is fine, but not while you're trying to identify whatever is going on with the rear...
* wheels checked over and restored, and fresh tyres fitted
* its worst at a constant higher speed
* creak from the front axle over large bumps
* tech that drove also commented it 'understeered a lot'
* No change in noise with speed change
First, the clunking/creaking from the front suspension is probably unrelated.
With the car in the air, in neutral, have you spun both rear wheels by hand? If a bearing is shot, you will likely feel a bump or grinding from the affected ball(s). As Ditto suggested, grabbing each rear tire (wear gloves) and trying to wiggle it from side to side can reveal bearing play.
Worrying about why the front end sometimes clunks or creaks is fine, but not while you're trying to identify whatever is going on with the rear...
11-21-2016, 09:45 PM
#14
Race Car
Is the exhaust stock or aftermarket?
11-22-2016, 08:06 AM
#15
* droning noise and slight vibration...coming from the rear of the car
* wheels checked over and restored, and fresh tyres fitted
* its worst at a constant higher speed
* creak from the front axle over large bumps
* tech that drove also commented it 'understeered a lot'
* No change in noise with speed change
First, the clunking/creaking from the front suspension is probably unrelated.
With the car in the air, in neutral, have you spun both rear wheels by hand? If a bearing is shot, you will likely feel a bump or grinding from the affected ball(s). As Ditto suggested, grabbing each rear tire (wear gloves) and trying to wiggle it from side to side can reveal bearing play.
Worrying about why the front end sometimes clunks or creaks is fine, but not while you're trying to identify whatever is going on with the rear...
* wheels checked over and restored, and fresh tyres fitted
* its worst at a constant higher speed
* creak from the front axle over large bumps
* tech that drove also commented it 'understeered a lot'
* No change in noise with speed change
First, the clunking/creaking from the front suspension is probably unrelated.
With the car in the air, in neutral, have you spun both rear wheels by hand? If a bearing is shot, you will likely feel a bump or grinding from the affected ball(s). As Ditto suggested, grabbing each rear tire (wear gloves) and trying to wiggle it from side to side can reveal bearing play.
Worrying about why the front end sometimes clunks or creaks is fine, but not while you're trying to identify whatever is going on with the rear...