Whining noise from the differential only between 34 to 42 MPH and under light load???
12-19-2007, 02:49 PM
#31
928 Collector
Rennlist Member
Rennlist Member
DAMN that is way above my abilities .... My brain goes to 10, yours goes to 11.
Here's from one of my previous posts...
.........
I recently used my digital voice recorder to record noises while driving. My car has a 220 Hz growl at 30mph but it goes away above and below that speed. It's quite faint and not that noticable.
I confirmed the pinion to ring gear as the source by using an Excel spreadsheet calculation to determine the gear teeth meshing frequency.
It's not that easy to guess the noise frequency, so I downloaded a shareware tone generator software program that I can adjust the frequency and amplitude. With Windows media player, I can play both the tone generator and the recorded sound track at the same time, adjusting the tone generator frequency to the tone of the gear noise.
If I playback the sound track on the computer speakers, it just sounds like noise. But with my high fidelity headset, I can hear the gear noise and resonance of the exhaust pipes quite clearly.
You could use this technique to isolate a wheel bearing noise. For the calculation, you'd have to know the bearing I.D. roller bearing diameter, tire size, speed, etc.
.............
.........
I recently used my digital voice recorder to record noises while driving. My car has a 220 Hz growl at 30mph but it goes away above and below that speed. It's quite faint and not that noticable.
I confirmed the pinion to ring gear as the source by using an Excel spreadsheet calculation to determine the gear teeth meshing frequency.
It's not that easy to guess the noise frequency, so I downloaded a shareware tone generator software program that I can adjust the frequency and amplitude. With Windows media player, I can play both the tone generator and the recorded sound track at the same time, adjusting the tone generator frequency to the tone of the gear noise.
If I playback the sound track on the computer speakers, it just sounds like noise. But with my high fidelity headset, I can hear the gear noise and resonance of the exhaust pipes quite clearly.
You could use this technique to isolate a wheel bearing noise. For the calculation, you'd have to know the bearing I.D. roller bearing diameter, tire size, speed, etc.
.............
12-19-2007, 03:49 PM
#32
Rennlist Member
Thread Starter
Bill,
Number 33 on the PSD picture shows a thrust washer. According to PET this washer is available from 1.8 to 2.2 mm. Could this be used for adjustments?
Do you think my noise could be caused by vibrations inside the differential?
Number 33 on the PSD picture shows a thrust washer. According to PET this washer is available from 1.8 to 2.2 mm. Could this be used for adjustments?
Do you think my noise could be caused by vibrations inside the differential?
12-19-2007, 04:03 PM
#33
Under the Lift
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Differential experts should jump in and help out here! These days my brain only goes to 7.
12-29-2007, 10:22 AM
#35
Racer
Hi guys,
it was me Schocki was referring to. Actually it didn't turn out ...yet. I'm still waiting for parts.
The play in the half-axles seems high to me. I can move the outgoing axle left about 1mm and richt maybe 0.5mm and that seems a lot. As soon as the parts arrive I'm taking things apart in a friendly independant Porsche shop, and see if I can stop the sound. Maybe it is the ring backlash, I'm not really sure.
The whining sound is just like Schocki said: only under partial load at 50-60km/h.
@Barry: can you maybe post or email the alignment spreadsheet you made? Thanks.
All the best,
it was me Schocki was referring to. Actually it didn't turn out ...yet. I'm still waiting for parts.
The play in the half-axles seems high to me. I can move the outgoing axle left about 1mm and richt maybe 0.5mm and that seems a lot. As soon as the parts arrive I'm taking things apart in a friendly independant Porsche shop, and see if I can stop the sound. Maybe it is the ring backlash, I'm not really sure.
The whining sound is just like Schocki said: only under partial load at 50-60km/h.
@Barry: can you maybe post or email the alignment spreadsheet you made? Thanks.
All the best,
