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limited slip friction modifier

  • Thread starter Thread starter 2nd Mustang
  • Start date Start date Mar 9, 2009

2nd Mustang

Founding Member
Feb 24, 2002
2,488
0
46
Southern California
Mar 9, 2009
#1
  • Mar 9, 2009
  • #1
I have a nine inch rear end with a limited slip 3.25. I don't drive this car every week, but a few months ago, I noticed a slight humming noise from the rear end after the car warms up. The rear end housing looked wet so checked the lower two housing bolts and they were loose. I tightened them up and added a little gear lube but the humming still persists after a few minutes of driving. It's not as loud as before, but still there.

I'm just fishing for possible answers so could it be old gear lube or lack of limited slip friction modifier? I've owned this car for about 7 years so I don't know how old the gear lube is. Thanks.
 

65ShelbyClone

Founding Member
Sep 9, 2000
4,675
38
119
Antelope Valley, SoCal
Mar 9, 2009
#2
  • Mar 9, 2009
  • #2
The friction modifier just ensures that the clutches in the LSD work properly and don't chatter. It doesn't affect lubrication of anything else and would not have anything to do with the humming.

At this point you may want to pull the chunk and have a look at the gears and bearings.
 

socalwrench

New Member
Mar 7, 2009
26
0
1
Mar 9, 2009
#3
  • Mar 9, 2009
  • #3
65ShelbyClone is right on, the friction modifier is simply for the correct operation of the LSD.

The humming noise is probably a worn out ring and/or pinion gear. If the oil level was low for a while, it may be time to check for bearings.
 
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