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Differential Noise-Bad Gear Mesh?

Old 02-25-2019, 12:10 PM
  #1  
aggiecoug
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Default Differential Noise-Bad Gear Mesh?

I recently had a shop replace my damaged ring and pinion, and when it went back together my rear end kept one of its more annoying symptoms-a loud whine on deceleration that peaks around 40 mph. It also gained a new whine on acceleration 35-40mph. The shop said they took it apart several times and could not correct the whine, and that I may need a new axle housing.

Before paying anything else, I'm hoping to get some educated opinions about what might be going on. I popped the cover off to look at the gear mesh, and while it doesn't look like a textbook example of proper gear alignment to me, I don't have the experience to differentiate between acceptable and poor alignment.

Below are pics of the drive and coast side of the gear. The color had been slightly enhanced to bring out the wear pattern, as gear marking compound + oily gears = a mess.



Drive side

Coast side
To the gear setup experts out there, how does this look? Would the gear setup be the cause of my whine, should I be looking for a junkyard axle housing, or could it be something else?

Thanks for your thoughts!
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Old 02-25-2019, 11:50 PM
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imp
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Originally Posted by aggiecoug View Post
I recently had a shop replace my damaged ring and pinion, and when it went back together my rear end kept one of its more annoying symptoms-a loud whine on deceleration that peaks around 40 mph. It also gained a new whine on acceleration 35-40mph. The shop said they took it apart several times and could not correct the whine, and that I may need a new axle housing.

Before paying anything else, I'm hoping to get some educated opinions about what might be going on. I popped the cover off to look at the gear mesh, and while it doesn't look like a textbook example of proper gear alignment to me, I don't have the experience to differentiate between acceptable and poor alignment.

Below are pics of the drive and coast side of the gear. The color had been slightly enhanced to bring out the wear pattern, as gear marking compound + oily gears = a mess.



Drive side

Coast side
To the gear setup experts out there, how does this look? Would the gear setup be the cause of my whine, should I be looking for a junkyard axle housing, or could it be something else?

Thanks for your thoughts!
Car model and type of axle? The best way to tell whether a gearset will trun quietly is to turn them by hand, by grasping the ring gear with a gloved hand, and turning back and forth, with the driveshaft dropped off from the pinion yoke. Wheels must be elevated, obviously. Even better, axles removed, as the added torque needed to rotate everything detracts from the ability to "feel" gear mesh.

The feel should be smooth in both directions or ring gear rotation. Any "scratchiness" or roughness felt means those gears will "sing". If they feel nice, doesn't mean bad bearings on either pinion or diff carrier are not allowing "mis-match" of gear teeth under load

Blaming the axle housing itself is ridiculous. Talk to a gear builder who understands this ****, if you can find one. (I'm one). imp
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Old 02-26-2019, 03:45 PM
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08'MustangDude
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A howl or whine during acceleration over a small or large speed range is usually caused by worn ring and pinion gears,
or if swapped, improper gear set up.

Look at the top picture, the left side of the teeth on the ring gear have some scoring. When a vehicle pulls a heavy load,
the pinion gear tends to ride on the outer portion of the ring gear. This will cause excessive scoring, evident on the outer
edges of the ring gear. The surface of the ring gear teeth should be smooth. If it looks like wood grain, with patterns of
scoring all across, this is NOT normal wear and the gear needs to be replaced. Normal patterns of wear for both the
gears is perfectly down the center of the gear teeth. If you see wear near the edges, or on alternating ends of the gears,
then there is an adjustment problem, or they are simply worn and it will whine on acceleration.
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Old 02-26-2019, 11:03 PM
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aggiecoug
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Thank you both for the insights. These gears are on a '14 GT's 8.8, for what it's worth. This evening I took a look at the factory ring gear that came off the car and saw the even, perfectly centered pattern you mentioned--nothing like what I saw on the new gears. I'll go back to the shop later this week with the photos and see if they'll admit they messed up and find out if their warranty means anything.
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Old 03-02-2019, 08:05 PM
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artsvettes73
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Gear setup is incorrect, pattern isn't centered.
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Old 03-03-2019, 02:14 PM
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08'MustangDude
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Yeah, I said that 5 days ago...
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