Rear differential hum

T

TonyLS

Active LVC Member
Joined
Jan 13, 2005
Messages
131
Reaction score
1
Location
Boston
2004 LS V6 with 25,500 miles.

Background:
When this car was brand new with only 600 miles it developed a rather loud humming noise in the rear differential when travelling at speeds between 50 and 55mph. Before and after this speed window the differential was quiet. Within the speed window, with the noise present, I could take my foot off of the gas and the sound would go away. The instance I pressed on the gas between 50 and 55 the sound came back.

Since the car was brand new the dealership ordered an entire rear end, they told me that this was an extremely unusual repair. Everything seemed to be fine after they swapped out the rear end.


So now after about 25,000 miles with the new differential I started to hear the humming noise again. Not nearly as loud, but the exact same symptons.
The car is still under warranty, I doubt that they will replace the entire rear end again. I guess they could go into the differential and replace the bad bearing, or whatever it is.

Has anyone had this problem? How many miles? What was the fix?

Any info or advice is appreciated.
 
My 2000 v8 has almost the same symptoms. I thought it was in the gearing though. It only happens when the rpms are low and im am going around the same speed as you.
 
A_Rome; How long has this been happening? has it gotten worse over time?
 
IIRC, there's a TSB for the drone/hum from the rear end on the '00 LSes (maybe '01s and '02s). It has to do with the half-shafts; they get replaced with a revised design, and the noise goes away.

That's not a known problem on later model LSes, though--they have the revised half-shafts. ToddG had this problem on his previous V6, but I don't remember what the diagnosis was; you might PM him.
 
Typical sounding symptoms of either a ring and pinion wearing out on the load side (not common) or a side bearing going out on the carrier (more common) It's usually the side bearing on the same side of the carrier as the ring gear as it takes the most load.
 
Thanks for the info, I'll have to ask ToddG about his experience. So I should push them to fix this rather than having them waive it off and telling me "Lets keep an eye on it to see if it gets worse" type of thing?. This is a very reputable dealership, they are excellent to work with. I have an appointment tomorrow.
 
Actually, my problem was not with the differential. It turned out to be a rear wheel bearing. The symptoms I had were a hum most noticeable between about 30 and 55 MPH. The pitch of the hum would vary depending on speed (higher speed, higher pitch, and vice versa).

I was told my my dealership's technicians that the differential was revised in the 2003+ models to overcome the drone/hum noise that was present in the 00-02 models. However, the wheel bearings across all years are the same, and they tend to give out. I took the tech for a ride, and he knew immediately what the problem was. It may be worthwhile for you to do the same ride-along.
 
a tip here to help pinpoint the location of the sound is to drive with the rear seats folded down. this makes the sound MUCH louder and makes it easier to tell if it's coming from the center (diff) or sides (wheel bearing) of the car. just FYI. and my 03 does the same thing.....it's the wheel bearing.
 
Thanks for the info, I will take it for a ride tonight with the back seats down to determine if it's coming from the wheels or at the center where the differential is. I already had a front wheel bearing replaced, however it didn't make the hum/drone sound as what I am hearing now in the back. But we'll see...
 
If it's a wheel bearing, you should be able to swerve the car to the left and right while it's making the noise and isolate it. If you swerve left and it goes away, it's the left wheel bearing....and vice versa. If it pretty well stays the same, it's probably in the diff. Just make sure you keep the power applied while you do this.

Just to add to this...if you swerve left and it gets worse, then it's more than likely the RIGHT wheel bearing...and vice versa.
 
Doesn't the fact that the noise goes away once I take my foot off the gas and it immediatly appears when I put my foot back on the gas prove that it's the diff and not a wheel bearing?
 
That sure indicates to me that it's ring and pinion or carrier bearings. It could also be a pinion bearing, but that should make noise all the time. However, it would be worth looking at...especially if you find a failed carrier bearing. The tests I mentioned are easy to do and worth the little effort involved before you tear into it. But I'm like you and betting it's in the diff.
 
TonyLS said:
Doesn't the fact that the noise goes away once I take my foot off the gas and it immediatly appears when I put my foot back on the gas prove that it's the diff and not a wheel bearing?
Click to expand...

Prove? No. But it may suggest it. I would definitely have the tech check both the diff and the wheel bearings.
 
Well, the dealership has my car and will be getting back Monday night. The service writer I had wasn't my usual guy who is top notch. He just called and said that the parts for the rear end problem/noise are on order and the car should be ready Monday night. So I guess I have to wait to really find out which parts they are replacing. But I'm sure they stock plenty of wheel bearings, must be the diff.
 
Just got my car back from the dealership, here is what was replaced to fix the rearend noise:

cup
cone
bearing asy - ball
gear and pinion asy

Service manager said they have done a few of these jobs. He said that the replacement parts have been redesigned so that they will not wear quickly. We'll see.

She rides great now. Man what a difference between the LS and the Sable loaner that they gave me! The LS is nice and tight, quick handling and responce.
 
Wow! I'm surprised they replaced the ring and pinion under warranty. Usually Ford has them replace the entire pumpkin.

Definitely sounds like you lost a carrier bearing...which is what we suspected.
 
You must log in or register to reply here.

Members online

No members online now.
Total: 97 (members: 0, guests: 97)
Back
Top