How to Silence Rear Axle Noise?

[Chistopher]

Hey fellas,

My 07 has a lot of noise coming from the back axle. Not red flag levels of noise, but a decent amount louder than my buddy's 06. I'm assuming this noise is due the age as the car has 130k on it. I've put a new sound system in the car so the next play is to reduce road noise.

Right now I figure I'll just use dynamat, but I don't know exactly where it'll work out best. Also if there's an easier solution that's not too much money, I'd be all ears.

Right now the cars a daily driver, so I'd like to keep it out the shop.

 

[Juice]

Describe said noise:
Under acceleration? Deceleration? Coasting? Turning?

I have my complete rear axle from my 07, and would sell cheap. Im in PA, if you are reasonably close, I can deliver it.

 

[07gts197]

If there’s noise it’s probably because something is wrong. Putting dynamat in is like putting a bandaid on a bullet wound. Is it gear noise or road noise? It could be something as simple as low tire pressure or bad bearings.


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[Chistopher]

It's just the faster the rear axle is turning the louder it get's, regardless of what revs the engine is at. It's the same noise the back axle usually makes in a car, just louder.

I know it's not the exhaust, and it's not the brakes or calipers, so I've narrowed it down to the axle itself.

If there’s noise it’s probably because something is wrong. Putting dynamat in is like putting a bandaid on a bullet wound. Is it gear noise or road noise? It could be something as simple as low tire pressure or bad bearings.


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It sounds a lot like road noise, the mechanic that the previous owner (10k ago) said it wasn't a major issue

 

[rocky61201]

My 1st guess is pinion bearing going bad. Can you grab hold of the pinion flange that connects to the driveshaft and check for any free play. If there isn't any movement it doesn't rule out the bearing is going bad. Bottom line is if pinion bearing is going bad you might as well rebuild the entire rear axle while you're in there.

 

[Chistopher]

My 1st guess is pinion bearing going bad. Can you grab hold of the pinion flange that connects to the driveshaft and check for any free play. If there isn't any movement it doesn't rule out the bearing is going bad. Bottom line is if pinion bearing is going bad you might as well rebuild the entire rear axle while you're in there.

Trust me, I'd love to rework the whole car from the engine to the wheels. I'm still in college though, so that's not quite an option, but when I graduate I've got a job lined up as a software engineer so I can afford to put more work into this thing. It looks like a good car to learn the ropes on.

I'll take a look at it when I get home. Anything else to look at while I'm under there?

 

[07gts197]

If it’s a hum then it’s wheel bearings.


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[Chistopher]

If it’s a hum then it’s wheel bearings.


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I guess it could also be described as a hum. How would I check other than by ear?

 

[skwerl]

For the investment of a couple hours and $40 of supplies (gear lube and Permatex), you can pull the rear cover and inspect the gears. Take note of excessive metal flakes in the oil or excessive wear on the gears. That's probably the easiest item to eliminate as a possibility. And I doubt the rear axle lube has ever been changed, so it needs to be changed anyway.

 

[rocky61201]

A sign of a bad wheel bearing in the front or back will get louder when entering a turn, like a freeway on-ramp or off-ramp so you are carrying plenty of speed. If the bad one is on the left side, then when turning right you are loading up the left side of the car and the bad wheel bearing will get louder. Reverse what I described if the bad bearing is on the right side of the car. Then you would be turning left.

If the noise is constant but gets louder with speed when going straight, then it could still be a wheel bearing, but likely it is one of the bearing's in the rear differential.

I've put 275k miles on my 06GT. I've diagnosed and replaced EVERYTHING at some point in time.

Last bit of advice. If it is a rear axle wheel bearing DO NOT replace with a standard over the counter replacement from PEPBOYS, AUTOZONE, ORIELLY's, etc. They are about 2 inches wider than the Ford Wheel Bearing and it is a 1 piece part that combines the bearing and seal. DO NOT use it!!!

Bottom line, if it bothers you that much, then rebuild/refresh the entire rear axle. It can be done in your garage on your day off for a couple hundred bucks. Rent the tools you need to save money if you have too. There of plenty of great you tube videos on how to rebuild a Ford Rear Axle.

 

[rocky61201]

Trust me, I'd love to rework the whole car from the engine to the wheels. I'm still in college though, so that's not quite an option, but when I graduate I've got a job lined up as a software engineer so I can afford to put more work into this thing. It looks like a good car to learn the ropes on.

I'll take a look at it when I get home. Anything else to look at while I'm under there?

Sorry I didn't see this post before I put in my last reply. I understand if you don't have a garage, that sucks. Like I said you CAN do it yourself in 1 day for a couple hundred bucks. That's better than waiting for it to get really bad over the next two months and having to pay a shop 2 thousand. I hope it works out for you and you find a way to get it done. Try to find a friend more knowledgeable who would be willing to do a ride along and tell you what the problem is for free. I'm in San Diego County for what it's worth. Always willing to help out an S197 member.
Go to a local car show and talk to the old guys. A rear axle is a rear axle. Make and model doesn't matter. They all work the same and have the same problems.

 

[Mach2burnout]

Do you know if all the parts in the rear are stock?


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[dark steed]

What tires do you have on it? I have gen 1 Nitto 555’s and they make so much noise my local rear end guy pulled a brand new bearing he had just installed because of the noise from the tires…


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[Chistopher]

I was talking to the previous owner and it seems the solution is simpler than I originally thought. They simply removed the factory rear axle sound proofing. Saves me a pretty penny. I'm assuming I install that under the rear seats?

 

[Bryce A]

I have an 07 GT and also have a noise in my rear axle. It had the noise when I bought the car with 68k miles and now it has 78k. I changed my diff fluid and it made zero difference in the noise. From what I've seen in the TSB's, some of these have noisy clutch packs and the only way to get rid of the noise is replacing the pack with the newer version.

 

[skwerl]

Bryce, welcome to the forum. I would recommend further diagnosis before you start throwing parts at it. Replacing parts is a very expensive diagnosing method.

Although the diff fluid change is a good move in any vehicle over 10 years old.

 

[Bryce A]

I'm not replacing my clutch pack if that's what you're thinking. Since owning the car, it hasn't gotten worse so I don't see the need. The TSB for the pack states that it being noisy does not affect the vehicles performance and it's still safe to drive.

 

[Juice]

A clutch pack will only make noise when turning sharp corners. Going in a straight line, the clutchpack is just along for the ride.

 

[Bryce A]

There is a consistent noise in my cars rear diff, regardless of turning or not. When I turn left, I get a louder hum. When I turn right, no hum, just the standard noise I hear from the rear. It's a rotational noise I hear all the time and I think if anyone else has this occuring, change the fluid, put in the friction modifier if your vehicle calls for it and see if it goes away, stays the same, or gets worse. Then you can further diagnose if there's a problem. Just remember - there's a TSB for rear axle whine. There's dampeners you can install or you can replace the clutch pack. If you are still unsure, take it to a shop that's specializes in rear diffs and ask if they've done other mustangs that have has this same issue.

 

[pass1over]

That sounds like classic symptoms of a wheel bearing going bad. Gets worse when you turn one way and not the other, in this instance, your right rear wheel bearing. You turn left, it's loading up that bearing and making more noise.

FWIW, I have 3.73s in my car and they are known to "sing" a bit while going down the road. What gears are in your car?