Who is running a aftermarket rear that is quiet?

[69x22]

Who is lucky enough to have a aftermarket rear-end that is wisper quiet?
Is it a 9", 12bolt, or Dana? Who built it? What brand of gears?
:disgusted:

[Z06vette]

I am...AFTER having the gears removed, putting in new ones (richmond double diamond in black box) And paying to have the new gears set up properly. I'm running moser 12 bolt with ford ends, 31 spline, wavetrac, 4.10s. Moser did send me a new gearset & install kit at no charge , but after paying over $3k for the complete setup, I paid nearly another $500 to reinstall new gears. They wanted me to remove the entire rear end, crate it up, and ship it back to them. That would be on my dime, and if was determined they were at fault, it would be fixed at no charge. That seemed ridiculouse to me, told them it would be cheaper & much less work to just buy new gears. So thats when they offered to send tme the gears & install kit. Its sucks, but its near whisper quiet now. Could have been worse, they could have just said F U, send the whole housing back or live with it. What setup are you running?
Scott

[67ragtp]

I am...AFTER having the gears removed, putting in new ones (richmond double diamond in black box) And paying to have the new gears set up properly. I'm running moser 12 bolt with ford ends, 31 spline, wavetrac, 4.10s. Moser did send me a new gearset & install kit at no charge , but after paying over $3k for the complete setup, I paid nearly another $500 to reinstall new gears. They wanted me to remove the entire rear end, crate it up, and ship it back to them. That would be on my dime, and if was determined they were at fault, it would be fixed at no charge. That seemed ridiculouse to me, told them it would be cheaper & much less work to just buy new gears. So thats when they offered to send tme the gears & install kit. Its sucks, but its near whisper quiet now. Could have been worse, they could have just said F U, send the whole housing back or live with it. What setup are you running?
Scott

Sad! This is becoming the norm. Gears are hit or miss, most being manufactured overseas now. I recently set up a 12 bolt wavetrac with US GEAR 390s, perfect pattern, howled like no tomorrow. Switched to Yukon Gear and Im real happy with the outcome. Might be worth while to pay for dyno service on a complete rear or center section, perhaps that will insure a quiet rear.

http://www.lateral-g.net/forums/showthread.php4?t=42701

The guys at moser laughed at me when I asked them who has the quietest gears, He basically said if you want quiet find a factory set. These are performance gears they will be noisy.

Good luck- Rich

[strtcar]

Not a peep from my Strange 9", bought it locally from strange about 6 years ago, replace fluid every 2 years (overkill) but its been perfect.

9"
Tru Trak
SS Axles
Not sure what gear they use.

[clill]

I had noisy gearsets a couple times. Then I found out I should not have used snythetic fluid from the start. Should have broken them in with non synthetic. Did that the next time and gears stayed quiet.

[GregWeld]

Had a LONG discussion about this with the Eaton guy -- absolutely NO synthetic gear lube! It's too slick. Hard to imagine but I gotta run with what the experts tell me.

[69x22]

I am...AFTER having the gears removed, putting in new ones (richmond double diamond in black box) And paying to have the new gears set up properly. I'm running moser 12 bolt with ford ends, 31 spline, wavetrac, 4.10s. Moser did send me a new gearset & install kit at no charge , but after paying over $3k for the complete setup, I paid nearly another $500 to reinstall new gears. They wanted me to remove the entire rear end, crate it up, and ship it back to them. That would be on my dime, and if was determined they were at fault, it would be fixed at no charge. That seemed ridiculouse to me, told them it would be cheaper & much less work to just buy new gears. So thats when they offered to send tme the gears & install kit. Its sucks, but its near whisper quiet now. Could have been worse, they could have just said F U, send the whole housing back or live with it. What setup are you running?
Scott

My 12 bolt came from Moser with Motive 3.55s. Those didn't make it to the end of the street without screaming at me. Moser wouldn't warrantee it because the rear sat for a year and a half while the car was being built. The next 2 sets were put in by Pyle Brothers, Hoosier 3.73s and Motive 3.73s, both were loud and got worse as time went on. The next set were used GM off Ebay (quietest so far). They had a slight whine between 45 and 50 but have gotten worse. I've never used synthetic throughout all of this.

[Vegas69]

You may want to look at how your rear end is insulated through the bushings. To have 4 sets of gears be unacceptable leads me to think there is another problem with the rear end or your expectations are to high.

[Vince@Meanstreets]

My 12 bolt came from Moser with Motive 3.55s. Those didn't make it to the end of the street without screaming at me. Moser wouldn't warrantee it because the rear sat for a year and a half while the car was being built. The next 2 sets were put in by Pyle Brothers, Hoosier 3.73s and Motive 3.73s, both were loud and got worse as time went on. The next set were used GM off Ebay (quietest so far). They had a slight whine between 45 and 50 but have gotten worse. I've never used synthetic throughout all of this.

How was it set up? What was your backlash? How about your pattern?

It's hit or miss on the specs that come out. Had a few with no pre load at all. I even polished the gears on a few richmonds and it seemed to do the trick.

[RBuhr69]

I just put in Moser 12 bolt with Richmond gears, Eaton Posi, non synthetic lube...I have a very faint noise at 70mph, but nothing I cant tolerate and it is very faint but can hear it..

[69x22]

You may want to look at how your rear end is insulated through the bushings. To have 4 sets of gears be unacceptable leads me to think there is another problem with the rear end or your expectations are to high.
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.

How was it set up? What was your backlash? How about your pattern?

It's hit or miss on the specs that come out. Had a few with no pre load at all. I even polished the gears on a few richmonds and it seemed to do the trick.

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.

[NvrDun71]

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

[Blake Foster]

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?

[Sieg]

The gear manufacturers blame it on the people setting them up and the people setting them up blame it on the gears.


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:

[Twoblackmarks...]

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?

[Vegas69]

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:

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

[69x22]

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?

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.

[WSSix]

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.

[4mul8ion]

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.

[Vince@Meanstreets]

Great post, you need to hang out more often.

[Sieg]

As it stands I have about $3800 to $4000 in this noisy piece of junk, and it still howls.
Sorry to hear it. :bur2:

My car is running silent OEM 3:31's in the original 12-bolt. The T56 mag needs 3:73's but this throw-the-dice noise issue isn't exactly motivational. :headscratch:

[HIFLYR]

I am glad this post was posted before I bought my rearend. I simply do not believe that if you buy a complete rearend from moser it should make noise because it is aftermarket. Moser should have complete control of their parts sourcing and ensure the end product is a good one when you buy a COMPLETE rearend. Yes there could be problems when sourcing parts from different places and assembling it yourself but not for a manufacturer of complete units.

[4mul8ion]

Setting aside the other design requirements, as far as axle noise is concerned, it takes three things to get axle noise. A source of the vibration to generate the noise, a path for the noise to take and a responder – or speaker – to make the noise audible to the driver.

The sources of the noise can come from the gear meshing but can also come from bearing faults as well. There are different mechanical vibration frequencies that can be the source of the noise depending on what is happening.

There are two paths for the noise to take and the associated speakers: through the suspension into the body that vibrates a body panel or forward into the driveshaft and that set off motions in the driveshaft that travels through the air into the vehicle cabin.

The classic gear noise that drives everyone crazy generally comes from vibrations generated by the first harmonic of the gear meshing that either travel through the suspension into the cabin or into the driveshaft and rings it like a bell. It generally occurs when either accelerating through the 45 – 65 MPH range or decelerating 65- 45 MPH. But not always.

Looking at the driveshaft path first, it is spinning hollow and is now commonly made out of aluminum with various OD’s and tube wall thicknesses depending on the manufacturer. Bare with me here – I’ll try to get to my point quick. It’s supported at one end at the axle and on the other end by the transmission. One end of it has to be able to translate in the vehicle fore/aft direction to allow the rear axle to move in the path dictated by the suspension. It has to take the engine torque, amplified by the transmission gear and sent it through to the rear axle through universal joints. The U joints are optimized to run an included angle between the transmission and driveshaft of no more than 3 degrees and, for best performance, an equal included angle of no more than 3 degrees to deliver smooth rotation from the transmission to the rear axle.

The point is that the driveshaft is allowed to move in its mounting and doesn’t deliver smooth power to the axle. The rotation accelerates and decelerates as the u joint rotates. The ring and pinion don’t mesh smoothly by themselves either. These accelerations / decelerations set up the gear mesh vibrations that forces the driveshaft into various resonant frequencies that you hear depending on the geometry of the tube and amplitude of the acceleration / deceleration of the rotation. The OD, wall thickness and length for a given material determines the bending frequencies and shell modes – or bell ringing – frequencies and the torsional frequencies of the driveline. Changing these dimensions move the resonant frequencies up or down in vehicle speed. Naturally, the OEMs try to increase these frequencies to mask the gear noise by other noises like wind or engine noises that aren’t so annoying or damp out the noise using tuned torsional dampers or inserts in the drive shaft tube. Neither eliminates the source of noise – it just moves the energy around. No free lunches.

The later 4th gen f-body driveshaft had an aluminum driveshaft with a larger OD and had both a tuned torsional damper that was pressed onto the transmission side slip yoke to damp out the torsional resonant frequencies. If you were to tap your knuckle along the axis of the driveshaft, there’ll be spots that will ring and spots that will go thud. Inside the tube, there are inserts to damp out the bending and bell modes of the driveshaft.

[GregWeld]

3:73's -- manufacturers will tell you that for some reason that ratio is "noisy". I've talked with Randy's Ring and Pinion (they're local for me) about this and that's what they told me. The Eaton rep told me the very same thing.


I frankly wonder how much of this is the transmission vs the rear end... the tranny in my '32 Ford is noisy... but I just chalk that up to the fact that the idiots at SAR probably charged me for a brand new one and installed a used one -- or that they ran it dry for a few days.... I'll replace it this winter.

The '32 runs straight cut quick change gears -- and they're noisy... so I might switch to helical cut versions when I do the tranny. s

[Vegas69]

Setting aside the other design requirements, as far as axle noise is concerned, it takes three things to get axle noise. A source of the vibration to generate the noise, a path for the noise to take and a responder – or speaker – to make the noise audible to the driver.

The sources of the noise can come from the gear meshing but can also come from bearing faults as well. There are different mechanical vibration frequencies that can be the source of the noise depending on what is happening.

There are two paths for the noise to take and the associated speakers: through the suspension into the body that vibrates a body panel or forward into the driveshaft and that set off motions in the driveshaft that travels through the air into the vehicle cabin.

The classic gear noise that drives everyone crazy generally comes from vibrations generated by the first harmonic of the gear meshing that either travel through the suspension into the cabin or into the driveshaft and rings it like a bell. It generally occurs when either accelerating through the 45 – 65 MPH range or decelerating 65- 45 MPH. But not always.

Looking at the driveshaft path first, it is spinning hollow and is now commonly made out of aluminum with various OD’s and tube wall thicknesses depending on the manufacturer. Bare with me here – I’ll try to get to my point quick. It’s supported at one end at the axle and on the other end by the transmission. One end of it has to be able to translate in the vehicle fore/aft direction to allow the rear axle to move in the path dictated by the suspension. It has to take the engine torque, amplified by the transmission gear and sent it through to the rear axle through universal joints. The U joints are optimized to run an included angle between the transmission and driveshaft of no more than 3 degrees and, for best performance, an equal included angle of no more than 3 degrees to deliver smooth rotation from the transmission to the rear axle.

The point is that the driveshaft is allowed to move in its mounting and doesn’t deliver smooth power to the axle. The rotation accelerates and decelerates as the u joint rotates. The ring and pinion don’t mesh smoothly by themselves either. These accelerations / decelerations set up the gear mesh vibrations that forces the driveshaft into various resonant frequencies that you hear depending on the geometry of the tube and amplitude of the acceleration / deceleration of the rotation. The OD, wall thickness and length for a given material determines the bending frequencies and shell modes – or bell ringing – frequencies and the torsional frequencies of the driveline. Changing these dimensions move the resonant frequencies up or down in vehicle speed. Naturally, the OEMs try to increase these frequencies to mask the gear noise by other noises like wind or engine noises that aren’t so annoying or damp out the noise using tuned torsional dampers or inserts in the drive shaft tube. Neither eliminates the source of noise – it just moves the energy around. No free lunches.

The later 4th gen f-body driveshaft had an aluminum driveshaft with a larger OD and had both a tuned torsional damper that was pressed onto the transmission side slip yoke to damp out the torsional resonant frequencies. If you were to tap your knuckle along the axis of the driveshaft, there’ll be spots that will ring and spots that will go thud. Inside the tube, there are inserts to damp out the bending and bell modes of the driveshaft.

Lot's of good thoughts here. OEM's spend millions of dollars making their parts mesh for the consumer. We slap some aftermarket parts on our 40 year old cars and wonder why it doesn't work out as we'd hoped. This is exactly where I was going with my original post. Four sets of gears and the noise is still there. It's time to start looking elsewhere for a solution.

I thought my Moser 12 bolt, 33 spline, true trac, with bolt in axles was quiet but to be honest, my exhaust was so loud who the hell knows. I will say that there was always a vibration in high gear in only a 300 rpm range that I could never completely get rid of the life of the car. I swapped out engine mounts, trans mounts, changed driveline angles. I finally just gave up as it was at like 85-90 anyway. I ended up with a rubber passenger mount and that made the biggest difference.

Greg, I told you not to put that POS TKO600 in your car. Nobody every listens.:lol:

[Sieg]

4mul8ion - Thanks for the info and education. :thumbsup:

Is it reasonable to assume the drive shaft is the primary speaker?

[4mul8ion]

4mul8ion - Thanks for the info and education. :thumbsup:

Is it reasonable to assume the drive shaft is the primary speaker?

No. There can be others. The path through the suspension resonating a body panel is much harder to deal with because you're trying to improve the ride and handling by using stiffer bushings. You give up isolation for improved handling. Locating the resonant panel is tough.

That's not all. You can still have amplification of the gear mesh vibrations by the suspension attachment brackets being forced into resonance going into the vehicle cabin. Or the OD and wall thickness of the axle tubes on a salisbury axle going into bending or torsion amplifying the mechanical vibrations going inside. The bushing can't effectively isolate an amplified signal.

My long winded point was that the OEMs spend a considerable amount of time desensitizing their new vehicles to the gear by looking at each and every component in it. I'm sure any of the OEMs who read this post will be overjoyed to hear that their hard work is paying off in strong quiet and durable performance in the field. They often don't get to hear that type of feedback.

There is no way any aftermarket company can compete with that resource requirement. But they have a good handle for their product performance in applications in other ways. Randy's, for example, suggest on their website, applications where OEM sets meet demanding customer applications better than the aftermarket. In particular, they say vans. I'm sure a call to any of the aftermarket companies to discuss a particular application would be useful if you get someone who's been around the block a few times. Did they optimize their aftermarket gear for an off road truck application or a car application?

The gear manufacturers spend a considerable amount of time optimizing their designs and processes too. OEM and aftermarket. It isn't just cutting slots in a ring of steel and slamming it into a case either. It can still be a bad gear for any or all of the reasons you had listed in your earlier post. Or the gear cutting summary wasn't optimized for the process it's in. Or bearing vibrations lighting up the driveshaft or coming into the cabin. Different vibration source, same resonant component will sound the same to the driver.

Point being is that it can be one or more of many things. "It's a bad build" or "It's a bad gear" is just the starting point. Important information to whoever is trying to diagnose what went wrong will want to know other things. Noise on acceleration or deceleration or both? What speed? What does it sound like? Was it always this noisy is it getting worse or did it just happen? Any pics of the pattern before or as it is now?

[Sieg]

I've been intrigued with acoustical damping ever since watching a show featuring an Aston Martin assembly facility on Velocity TV where an "engineer" was strategically applying a material similar to Dynamat Extreme in lightening bolt and wave shapes on interior cabin panels. I've always wondered how much science was behind their application considering the sophistication of their engineering.

I finally found a picture (and a great tour of the facility) tonight.

http://www.speedhunters.com/wp-content/uploads/2013/08/Aston_Martin_Gaydon-007.jpg

On these Vantage chassis I was interested to see these reinforcing strips added to the interior, applied as a result of noise, vibration and harshness studies to improve the characteristics of the chassis.

http://www.speedhunters.com/2013/08/aston-martin-at-gaydon-the-dream-factory/

[Twoblackmarks...]

Personaly I dont mind some whine, it makes the car feel more "racier" :D As long it is not too much.

I would think leaf spring transfer more sound than 4-link, soft mushy bushings MUCH less or zero sound vs. urethane and such. Frame car vs non frame etc..

I dont think my 87`Olds 442 8.5" 3.73 was very "developed" by GM to be honest. But it has a very "quiet chassis" that is forgiving for everything in sounds. -Super sweet car by the way

78 Camaro With 2.42 -No sound. Put in a used 3.73. Some mild sound when hanging on gear if i remember correct -could be the pinion bearing, or faulty setup, (also had been used...) even when set up by professionally. But to be honest I just think the aftermarket has a little less quality in it, or sound is not their ultimate deciding factor for the parts, but it still is somewhat weird I think, but the parts for US cars are really cheap to buy, so that explains atleast a portion of it. -For many types of parts..

If you ultimately want a quiet ride, install mushy bushings in everything, so they absorb everything you dont want to hear and feel, and lots`o sound deadening. I think that Cures most sounds.. :D

I work With New cars, and they are very sensitive to tire noise, out of round, sounds from drivetrain. If you take the Wheels of an old impala that glide like an boat at 100mph, they could be "oval" without feeling it, put them on a New car and it would feel horrible at 40-50mph and may make a LOT of tire noise.

Because every year they get harder bushing, more Direct mounting in body, lighter spindles, shocks and springs etc.

Now it is really good for driving to get less unsprung weight, but at the same time that unsprung weight act as an vibration/torsional damper, and usually the lighter/less mass an vibration damper have, the worse it "Works"

Since it ability to absorb vibrations, and even sounds lessens, and the more sound and vibrations then go through the modern hard bushings into the body and to the driver in one way or another.

Now I wrote much more than I was going to, I still think rear gears should be somewhat quiet, Stock or not, Depends somewhat though, what type and such. My Moser makes some sound, but not more than my exhaust, so dont know at the moment, and I am ok With it too, so it does not really matter, it is a Hot Rod, not a Rolls Royce :D

4mul8ion Has great Points.

Here we have a lot of modified cars like Voyager type cars With removed rear seat and changed carpets and different stuff, (because of TAXES!) Many of those complain about noises from everything, since the rear compartment now acts as a huge speaker.

This may be a messy post without much answer, but I still post it, and se what happens :P

[chr2002ca]

I've purchased 2 new complete 12-bolt rear setups from Moser for my '69 Camaro. The first was a 30-spline unit with Eaton posi and 3.42 gears. It made a little bit of noise after about 3000 miles but it wasn't too bad and I didn't really notice it much. The 2nd unit I purchased which is currently in the car is a 33-spline TruTrac with 3:42 gears again. It's perfectly quiet right now, but it only has about 550 miles on it. Time will tell. If it develops a whine, oh well, it doesn't really bother me. I have sound deadener laid down all the way to the back of the trunk, so maybe that helps.

[Boostable]

My Moser is pretty quite!! But then again Im still pushing the car around :)

In all seriousness, I hope there is not an issue as with some of you other guys I have had mine awhile, and will be more then a year before she see's the road from time of purchase.

[cluxford]

Strange locker in mine
35 spline
355 gears

can't hear anything over the roar of the 632 cube BBC running through twin 3" pipes and single magnaflows

[4mul8ion]

I've been intrigued with acoustical damping ever since watching a show featuring an Aston Martin assembly facility on Velocity TV where an "engineer" was strategically applying a material similar to Dynamat Extreme in lightening bolt and wave shapes on interior cabin panels. I've always wondered how much science was behind their application considering the sophistication of their engineering.

I finally found a picture (and a great tour of the facility) tonight.

http://www.speedhunters.com/wp-content/uploads/2013/08/Aston_Martin_Gaydon-007.jpg



http://www.speedhunters.com/2013/08/aston-martin-at-gaydon-the-dream-factory/

Very cool.

There's probably quite a bit of science behind those shapes. Check out this video that shows a flat plate going into motion at various frequencies.
wvJAgrUBF4w

[4mul8ion]

...
Here we have a lot of modified cars like Voyager type cars With removed rear seat and changed carpets and different stuff, (because of TAXES!) Many of those complain about noises from everything, since the rear compartment now acts as a huge speaker.
...


That's a great point. I'll be running 3.55s from us gear and I don't remember what was put down for lining my trunk.

[Sieg]

If my post was cool........your's ranks as Ubercool!

It would be interesting to apply sections of Dynamat to the underside of the test sheet to see how it impacts the patterns.

Flat plate in set gauges is one thing, plate formed by stamping has to be an entirely different animal.

Are there sensors that can be applied to plate to measure frequencies?

Thanks for the education!

[4mul8ion]

Thanks. This has been a fun discussion but apologies to 69x22 for pulling the topic of this post not just into the weeds but now through the weeds, through the guard rail and halfway into the corn field.

You're absolutely right. Formed steel is completely different. With different boundary constraints, bends and dimples, you can change the performance of the panel. They test it by having something apply a known force and measure the response using an array of accelerometers to measure the response.

http://www.pcb.com/portals/1/Images/Auto_Images/Modal.jpg

Dynamat has done something to determine the effects of their acoustic material to the patterns. Look at what they say for their XTreme product.
http://www.dynamat.com/technical_specs_dynamat_xtreme.html

I'm not sure what the effective absorbing range it can cover but for gear noise it needs to be most effective in the 300 - 600 Hz range to absorb gear mesh frequencies. That product may only be effective at absorbing lower road noise related frequencies.

Not sure on that.:drowninga:

[4mul8ion]

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?

The micro polishing process is just a tooth surface finish refinement only. It is supposed to polish out the cutter marks left over from manufacturing the gear. Classic gear noise comes from errors in the tooth profile as the teeth mesh together. If there is a tooth surface finish problem it will generally sound like a jet engine in the back. Very high frequency.

To make a gear, you have to turn the forgings, cut the teeth on the pinion, cut the teeth on the ring gear, heat treat quench and temper both, hard finish the bearing on the pinion and finish the bore and backface on the ring gear. Then hard finish the teeth by either lapping a pinion and gear together or grinding the tooth profile of each member.

As the cutter wears, the tooth profile changes and the cutter no longer cuts the part but starts to tear material off leaving a scratchy tooth surface. You can compensate for this cutter wear by adjusting the machine but if the cutter is too worn out, you're out of adjustment, the tooth geometry becomes less than ideal, the ridges are too deep and the hard finishing process isn't as effective.

Check out the video library of Precision gear explaining the gear cutting process in Chapter 4. Warning: terrible sound.
http://www.precisiongear.com/pgmanvideo.htm