The first set made noise during acceleration, the middle two were on the coast side, now the last set is on the acceleration side between 45 and 50 mph. All of them had noticeably gotten worse with time. The rear has Delrin bushings, the car has full exhaust and a nice sound system. So my expectations maybe a little high.

I set the GM gears up myself being they were used so I went with .011 on the backlash. The pattern was a nice oval low on the tooth. I plan on trying a pinion shim that will pull it out another .002. If that doesn't work I will try a set of Richmond gears.
I know it's a hit or miss with aftermarket gears. I'm just amazed that in 2013 the aftermarket can't produce gears that are for the most part "quiet". The gear manufacturers blame it on the people setting them up and the people setting them up blame it on the gears.

AAM gears set up by Pyle Bros should do the trick IMO

We have sold a lot of rearends. Strange and Currie, and Rons Rear ends, we have seen issues with Strange and Currie none with Rons, the biggest issue we have seen is with 3:73 gears.
Currie suggests 80-140 GL5 gear oil
Here is the deal, My Nova, My Camaro, both have run synthetic since day 1, neither got the "Proper break in" and NEITHER make a sound. I know that only confuses the issue.
We did one and it sounded like you were dragging a cat behind you, yes the MFG said send it back, and yes they changes the gears to 3:89's (from 3:73)but I too am with everyone else, why should the Customer(or shop) have to cover all the costs? the second set was only a bit better. now what???
HOW is it that the OEM's can do THOUSANDS of gears a DAY and not have one that makes noise, and the aftermarket we are just to put up with it.???Oh yea you have the option of spending another 300 to have them micro polished still there is no Guarantee they will not be quiet....... Why NOT?
Riddle me that?

It seems to be a common problem no matter the industry.........in my 36 years of flooring, carpet for a commodity example since it is a relative no-brainer to install PROPERLY just as setting up Ford or Chevy rear end gears is, the manufacturer more often than not pointed the blame at the blue collar worker first (we all know they don't possess fancy college degrees.....) when more often than not it was a simple manufacturing tolerance defect due to numerous cost saving measures (opportunities) implemented in their processes.

The reason for the excessive noise needs to determined and documented and thrown back in the manufacturers court. IMO - It creates an opportunity for a manufacturer stand above the rest. A set of GM 12 bolt gears is around $325 + labor to have them set up in my case........if I had a guarantee that a $525 set of gears would be OEM quiet it would be a relatively easy decision.

Why could GM make them quiet back in the 60's and in today's hi-tech world the manufacturer can't match 60's era production quality?

Are the noise issues more common in Ford vs GM housing designs or low vs tall gear ratios?

Inferior:
Materials quality?
Milling specs?
Milling equipment?
Finishing process?
Carriers?
Housings?
Mechanical noise?
Harmonic noise?

What causes the issue?

:sieg:

That is a good question, the only time a Stock differential makes sound, is when it is broken in one way or another..

Standard cars With 4.11++ do not make sound either.. European rear Wheel drive cars With small engines has 4.xx and upwards, they are smaller diameter ring gear, so they are "slower", but no sound.

I had an 3.73 8.5" that was Stock and abused, no sound.

How is the markings on an Stock rear end that is quiet vs "by the book" markings?

And who makes the gears for the OEMs?

If I had to guess, horsepower and the material used to hold up to the abuse. We are using OLD technology that needs to hold up to nearly twice the power it did 30-40 years ago.

That's what I found building my car. Every step I took to increase performance resulted in more noise, more maintenance, and less reliability.

New OEM stuff has been engineered from day one to be quiet and live at the specified output.

I still think a rear should be reasonably quiet. It may come down to finicky specs due to more aggressive material. I don't know, someone will figure it out with their pocket. Glad it's not mine. ha

Well put.
ZR1s, ZL1s, diesel trucks, and plenty of others are all very capable of being hard on rearends, but they don't make noise. If they did, they wouldn't be able to sell them.
Automobile manufacturers cannot afford to have their parts manufactured from companys that are taking short cuts then blaming it on them. I don't think it would cost much more to make a set of gears that could hold up and be quiet. I would have gladly paid it already. As it stands I have about $3800 to $4000 in this noisy piece of junk, and it still howls.

To further confuse the situation, I've done numerous C5 rear ends. It was easiest to buy the rear end housing with gears already setup. I typically bought from DTE only. All I ever did was slide it onto the transmission. I used Red Line Oil in every one just as DTE said to. Not a single one made noise.

I've set up a few solid axles as well. Some made noise others made none. Luckily, none were terrible. My own car makes a little bit of noise. Not enough to bother me as I have no AC so the windows are down. I may change my mind once it keep the windows rolled up though.

I'm with the rest of you though, it really makes no sense that today, with all the advancements we have in manufacturing and technology in general, that gears still whine when set up according to the manufacturer's instructions. Yet, OEM gears that handle tremendous power don't make a sound. Many of these OEM cars make more power than I ever will too. Something doesn't add up.

It would be great to be able to talk to the person or people that actually set up OEM gears to know the process and how they compensate for different tolerances to achieve a quiet rear end. I think it would make for a good magazine/online article.

In my opinion, I don’t think there is a mystery about the differences between OEM and aftermarket performance.

Here’s why.

It boils down to a balanced system design and vehicle integration – the OEMs have design control, the aftermarket does not. The OEMs can determine overall system strength/ durability and noise performance and roll down the specs for each of the driveline components accordingly. They’re responsible … or delegate responsibility to assemble each new component into various new sub assemblies with optimized processes for a given axle and driveshaft. The suspension design needs to be figured out and sourced. The transmission specs determined and sourced. Then it all has to play nice with each other under variable operating, manufacturing, and environmental conditions over a 10 to 15 year service life with no loss in performance and minimal service requirements within a given price point for each sub assembly.

Piece of cake. What do we do after lunch today?

On the oem side - regardless of which vehicle manufacturer it takes hundreds if not thousands of man hours to integrate a common gearset family into multiple vehicle platforms. Example, GM’s 8.5 10 bolt goes into pickups, SUVs and vans. It used to go into the B body, G body, 2nd gen F-body etc. Each has its unique needs to meet the performance requirements the vehicle designers want out of their vehicle. For economy of scale purposes they limit the number of ratios to make the number of combinations manageable to validate the total vehicle design for strength / durability / noise performance and fuel economy within the market window.

The aftermarket has to supply a general application gearset that has to go into off road trucks with big knobby tires, replacement gearsets for stock cars and trucks and high performance muscle cars. They have to make it easy for an unknown end user to assemble into components with unknown age and condition. They have to reverse engineer the specs that each OEM has created.

The GM 8.5 10 bolt has been in production from the early 1970’s and continues to this day with improvements as the 8.6 currently installed in half ton trucks, utilities and vans. 40 + years of applications on one axle size for one vehicle manufacturer. Now, GM had gear ratios available from a 2.41 to 4.56 using different carrier breaks. The aftermarket manufacturer needs to decide which of those OEM ratios will sell and which ones won’t and at what price point. They also need to decide what else to offer in the higher numeric ratios as the end customer re gears their truck / car for performance modifications and at what price point.

GM also has the 7.5, the 14bolt semi float (9.5), the 14 bolt full float plus the new stuff on the C5 / C6 / Holden cars / New Camaro, Etc to cover. GM isn’t the only vehicle manufacturer. There’s Ford, Chrysler, Toyota, Nissan, Suzuki cars, trucks and vans to consider.

Once the “what” to make is determined, now the “how” to make it begins.

Great post, you need to hang out more often.