Discussion
I recently bought a 2002 996 c4. I find that when I am driving between 50 and 60 mph there is a high pitched whine coming from the rear of the car. I recently had the car in for a service at 23000 miles and reported the noise problem. Firstly the main dealer said that the rear main oil seal was leaking and that could be causing the noise. A few hours later they called to say that the diff needs replacing. I have spoken to a couple of independents on this and they have never known a diff need be replaced after so few miles.
Can anyone shed any light on what the noise might be?
Can anyone shed any light on what the noise might be?
Maybe it's fairly continuous but more noticeable on a light throttle when background sounds are less? Hmmm Difficult to say without hearing it (!) but if the noise remains as a constant fairly high pitch hum regardless of when revs rise and fall, and doesn't change when speed changes either, I'd add an unhappy fuel pump to a list of possibilities. Doesn't have to make the engine cut out for a 911 fuel pump to be noisy like you describe. I'd be very wary of the diff idea without confirmation from a couple of indies, but the OPC (kerching) may be right. I'm not a techie but have managed to hear just about every 911 noise
Where's ninemeister when you need him - being at the wheel of a 400 bhp 911 at a certain Porsche event is no excuse
Where's ninemeister when you need him - being at the wheel of a 400 bhp 911 at a certain Porsche event is no excuse
The car was examined by a well know independent in Leeds before I bought it, they are adamant that there is nothing wrong with the diff and thay have never known one need replacing. Trust me to have bought the only lemon out there.
The car is still with my local OPC having been serviced etc, I will be collecting ot sometime this week. Hopefully huge bill are not around the corner.
Cheers for the help.
The car is still with my local OPC having been serviced etc, I will be collecting ot sometime this week. Hopefully huge bill are not around the corner.
Cheers for the help.
AndyL72 said:You did say about those speeds below, but knowing now it's 'restricted' to between 50 and 60 kills the noisy fuel pump option. If it was the diff it would be unusual to happen over such a restricted range but possible I guess. It sounds like a resonance now. Hopefully one of the indies will sort you out at reasonable cost.
sorry turbobloke, forgot to mention that the noise only occurs between 50 and 60 mph, although if you are gunning it then the sound is completely drowned out.
Once had a weird, faint, intermittent metallic knocking sound from the back of the car, it always disappeared when a techie was riding passenger to listen to it. After several such test drives and putting the car on a ramp I'd almost given up, then by chance it got hoisted on a four poster with the wheels on rails and everything including the suspension was sitting down like it is on the road - when it became clear that an OPC (that shall remain nameless) had re-fitted the rear anti-roll bar upside down and it was coming into contact with the centre longitudinal gearbox casing rib, grrrrr. Took minutes of labour and a few quid to sort.
I initially thought it might be a resonance problem from a worn bearing, especially as the 50-60 mph window is probably the speed at which most drving has been done. The tyres are below the OPC recommended tread depth of 3mm (approx. 2.3mm), could this have any bearing on my problem?
AndyL72 said:
I initially thought it might be a resonance problem from a worn bearing, especially as the 50-60 mph window is probably the speed at which most drving has been done. The tyres are below the OPC recommended tread depth of 3mm (approx. 2.3mm), could this have any bearing on my problem?
Unlikely, although I would consider getting the wheel balancing checked.... It's cheap, and a rolling imbalance can set up resonant vibrations.
Are they saying it's the gears or a bearing in the diff? Different symptoms and diagnostics for each. If it's the diff I would imagine the problem can be altered by throttling on and off at the affected range (You'll be taking up the backlash in the diff gears. If it's a wheel bearing, the sound shouldn't alter as much.
Fuel pumps etc are unlikely as the fault is speed dependant, not rev dependant. That means the problem is at some point after the clutch.
Tricky to pinpoint without hearing it, but if the independant say's it's not the diff, then it's unlikely to be the diff
AndyL72 said:
I initially thought it might be a resonance problem from a worn bearing, especially as the 50-60 mph window is probably the speed at which most drving has been done. The tyres are below the OPC recommended tread depth of 3mm (approx. 2.3mm), could this have any bearing on my problem?
I had a graoning noise from the back of my 993tt when the tyres were at their wear limit. Changed the tyre and the problem went away. If you have a chance of changing the back wheels with a different set that would eliminate this issue. Doesn't matter what tyres go on the back for this kind of test.
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