Notices
996 Forum 1999-2005
Sponsored by:

Low pitch hum/drone at 55mph

Thread Tools
 
Search this Thread
 
Old 06-07-2010, 10:35 PM
  #1  
Liceman
Instructor
Thread Starter
 
Liceman's Avatar
 
Join Date: May 2009
Location: Cleveland, OH
Posts: 105
Likes: 0
Received 0 Likes on 0 Posts
Default Low pitch hum/drone at 55mph

Over the past ~2 months I've noticed a low pitch hum/resonant drone from the rear of the car that only is audible from about 55mph to 62mph. Not related to throttle position nor clutch position from my tests. Is there with coasting at that speed, accelerating through that speed range, and decelerating through that speed range. I have had absolutely no vibrations or driving issues at all (knock on wood.)

Tire pressures look fine, and I have not noticed any vibration or wobble.

Any ideas? Wheel bearing maybe? Was planning on having it serviced for 45k maintenance soon.

Thanks for reading
Old 06-07-2010, 11:01 PM
  #2  
RPMulli
Banned
 
RPMulli's Avatar
 
Join Date: Apr 2010
Posts: 1,552
Received 48 Likes on 27 Posts
Default

wind?
Old 06-07-2010, 11:33 PM
  #3  
Pac996
Drifting
 
Pac996's Avatar
 
Join Date: Dec 2009
Location: Aiea, HI
Posts: 2,919
Likes: 0
Received 3 Likes on 3 Posts
Default

Eh mention it during servicing but might just be the tires like to make noises at that speed.
Old 06-08-2010, 08:40 AM
  #4  
Barn996
Race Director
 
Barn996's Avatar
 
Join Date: Sep 2007
Location: Kittery, Maine
Posts: 11,801
Received 14 Likes on 12 Posts
Default

I agree with the tire comment from PAC996. How many miles on the rears, any cupping or uneven wear?
Old 06-08-2010, 10:19 AM
  #5  
chsu74
Rennlist Member
 
chsu74's Avatar
 
Join Date: Oct 2006
Location: CT
Posts: 9,615
Received 312 Likes on 260 Posts
Default

Upgrade exhaust to FisterDs?
Old 06-08-2010, 10:44 AM
  #6  
SH || NC
Drifting
 
SH || NC's Avatar
 
Join Date: Sep 2008
Location: Cary NC
Posts: 3,049
Likes: 0
Received 0 Likes on 0 Posts
Default

These are all guesses
  • wheel bearing
  • time for fresh tranny fluid
  • low tire
  • loose exhaust clamp / bolt
  • pulley bearing

GL
Old 06-08-2010, 10:58 AM
  #7  
Macster
Race Director
 
Macster's Avatar
 
Join Date: Sep 2006
Location: Centerton, AR
Posts: 19,034
Likes: 0
Received 252 Likes on 222 Posts
Default

Originally Posted by Liceman
Over the past ~2 months I've noticed a low pitch hum/resonant drone from the rear of the car that only is audible from about 55mph to 62mph. Not related to throttle position nor clutch position from my tests. Is there with coasting at that speed, accelerating through that speed range, and decelerating through that speed range. I have had absolutely no vibrations or driving issues at all (knock on wood.)

Tire pressures look fine, and I have not noticed any vibration or wobble.

Any ideas? Wheel bearing maybe? Was planning on having it serviced for 45k maintenance soon.

Thanks for reading
Wheel bearing has to be at the top of the list.

Sincerely,

Macster.
Old 06-08-2010, 12:40 PM
  #8  
03911TT
Instructor
 
03911TT's Avatar
 
Join Date: May 2010
Location: Orlando, Florida
Posts: 213
Likes: 0
Received 1 Like on 1 Post
Default

I noticed something very similar prior to replacing my tires. Replaced tires and the sound went away. Could be you need new ones?
Old 06-08-2010, 12:56 PM
  #9  
Erik@GBox
Former Vendor
 
Erik@GBox's Avatar
 
Join Date: Oct 2009
Posts: 422
Likes: 0
Received 2 Likes on 2 Posts
Default

Well I hate to be the one to have to give you what may or may not be bad news here, but this sounds like it may MAY, be the internal sealed bearings for your gearbox. As they wear out the races they tend to sound just like what you describing. If this is the case it will continue to get worse and potentially more expensive. If you end up ruling everything else out this is probably the culprit.

Let me know if I can be of any help to you with this, if it does end up being the problem. These are a bit tricky to rebuild. We do them all the time though.

Warmest Regards,

Erik Johnson
GBox Performance Transaxle
(303) 440-8899 work
(303) 895-4828 cell
www.gboxweb.com
Old 06-08-2010, 01:10 PM
  #10  
fbgh2o
Odd Posts
Rennlist Member
 
fbgh2o's Avatar
 
Join Date: Dec 2007
Location: Ottawa, Ontario
Posts: 3,633
Received 51 Likes on 27 Posts
Default

Is it worse under acceleration versus at speed? If worse under acceleration loads that is indicative of transmission issues, but if it is constant, I would look at wheel bearings and tires.
Old 06-08-2010, 06:31 PM
  #11  
Liceman
Instructor
Thread Starter
 
Liceman's Avatar
 
Join Date: May 2009
Location: Cleveland, OH
Posts: 105
Likes: 0
Received 0 Likes on 0 Posts
Default

Thanks for thoughts so far.

It is constant at those speeds, independent of throttle or clutch. (ie NOT worse with acceleration) I'm 4th owner of car but second owner on these tires... I'll look into their age/wear...
Old 06-08-2010, 11:09 PM
  #12  
Pac996
Drifting
 
Pac996's Avatar
 
Join Date: Dec 2009
Location: Aiea, HI
Posts: 2,919
Likes: 0
Received 3 Likes on 3 Posts
Default

Since you first mentioned it always being a specific speed on and off the gas that's why I'm figuring tires. Most bearings I've had throwing trouble at me would change noise or completely quit making noise cornering and accelerating. Bearings when bad are going to be putting off much more heat than standard operating temps. You can feel hubs temp by feeling the wheel since they are mated and the heat will pass directly into the wheel. If you dearly regret touching the wheel its a good bet your bearings are bad.
Old 06-11-2010, 01:35 PM
  #13  
Liceman
Instructor
Thread Starter
 
Liceman's Avatar
 
Join Date: May 2009
Location: Cleveland, OH
Posts: 105
Likes: 0
Received 0 Likes on 0 Posts
Default

Wheels did not feel hot today after a 10 minute highway drive.

I did notice today that the drone/hum is also audible again at 70-72mph. So for those of you keeping score, it is noticeable at 55-62mph, then again at 70-72ish.
Not sure that this helps, but I figured I'd mention.
I'll have it looked at soon
Old 06-12-2010, 03:24 PM
  #14  
yasuro
Pro
 
yasuro's Avatar
 
Join Date: Mar 2008
Posts: 714
Likes: 0
Received 0 Likes on 0 Posts
Default

I have a similar noise at similar speeds. It's more noticeable on concrete roads vs. asphalt. After much road testing and checking, I think it's my worn front tires. They are not close to the wear markers, but are pretty worn. Time to order a set of HTZ IIIs
Old 06-12-2010, 04:12 PM
  #15  
Barn996
Race Director
 
Barn996's Avatar
 
Join Date: Sep 2007
Location: Kittery, Maine
Posts: 11,801
Received 14 Likes on 12 Posts
Default

Good selection, great price and tire.


Quick Reply: Low pitch hum/drone at 55mph



All times are GMT -3. The time now is 03:16 PM.