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Any gear can be noisey if there's a problem. Problems are not always with the gears themselves, or even from the chuck. But - if there are not other issues, and they are broken in proerly, no gear ratio in and of itself will be noisey.

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The wrong pinon angle can cause a perfectly setup rear to howl.

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That's BS.
The gears aren't set up properly.
He's blowing smoke at you.
Need to find someone else that knows what they're doing, and talking about.
When i first started out as an auto mechanic, i worked at a shop doing differentials, here in my city.

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The other common Fallacy is that the lower you go the more they will whine, BULLS$heet I say. I have run gear sets as low as 5:13's in a street car that were quiet as a church mouse. I've run 3:91's, 4:10's, 4:30's, 4:56's, 4:88's and 5:13's. ALL QUIET noise wise WHEN SET UP PROPERLY. IF one is talking about special RACE only sets that could be a different story.

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And it is the same guys that can't get the gears to be quiet that can't get a 8.75 to last behind a slant 6. IT IS ALL IN THE SET UP!!!! Some guys break them time after time after time and say the rear is junk, then other guys set them up and they last for really long times. I am shocked at how many shops I have seen guy replace a pinion seal on a crush sleave rear and just tighten the nut with a big ole impact, there are not a lot of guys who reeeeeealy understand how to set up a hypoid gear.

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That's BS.
The gears aren't set up properly.
He's blowing smoke at you.
Need to find someone else that knows what they're doing, and talking about.
When i first started out as an auto mechanic, i worked at a shop doing differentials, here in my city.

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The other common Fallacy is that the lower you go the more they will whine, BULLS$heet I say. I have run gear sets as low as 5:13's in a street car that were quiet as a church mouse. I've run 3:91's, 4:10's, 4:30's, 4:56's, 4:88's and 5:13's. ALL QUIET noise wise WHEN SET UP PROPERLY. IF one is talking about special RACE only sets that could be a different story.

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And it is the same guys that can't get the gears to be quiet that can't get a 8.75 to last behind a slant 6. IT IS ALL IN THE SET UP!!!! Some guys break them time after time after time and say the rear is junk, then other guys set them up and they last for really long times. I am shocked at how many shops I have seen guy replace a pinion seal on a crush sleave rear and just tighten the nut with a big ole impact, there are not a lot of guys who reeeeeealy understand how to set up a hypoid gear.

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You mean torque wrenches are not optional?

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There are particular gear sets than will be noisy, no matter the set-up. But that is more brand or batch specific, than ratio specific.

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I have a 3.55 gear set in my Challenger, every part is new and was bought from Doctor Diff and doe`s not howl at all.
I have 5000 miles on the setup.

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There are particular gear sets than will be noisy, no matter the set-up. But that is more brand or batch specific, than ratio specific.

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I agree with this. Most gears will not make much noise if set-up right. But I have seen some that make noise (not alot of noise but some) and they were done by good shops. Working for a Dodge dealer I can tell you I remember a truck that a customer complained the rear was noisey. It was a brand new truck with the new to Dodge "American Rear" and this was around 2005 to 2008 as I dont remember which year. I ended up replacing the ring and pinion and the pinion and carrier bearings as per the Mopar tech adviser and it was no different when I was done. And we had the proper tools for it since we were a Dodge dealer. It was not alot of noise as it was a small whine at about 55 mph. In fact most people would not even complain but this guy must have drove this speed alot. So in the long run Mopar had me replace the full drum to drum rear and recheck all the settings including pinion angle which made no difference as it still had some noise. I do believe the whine noise in the complete new unit did happen at a slightly lower speed. In the end the custumer was told that small whine is normal as it was and as I said most people like you all and me would have never even thought it was noisey enough to complain about. The guy took the truck happy with us as he saw me replacing the complete unit because the service manager brought him in the shop so he could see for himself we replaced the drum to drum unit. Ron

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They had to do this with my 03 Ram with the 9.25 SG. They rebuilt the original one with all new stuff and it still was noisy. It sounds like it was similar noise wise to yours and had the dealer not jerked me around on some other issues I would likely never have put in a claim, but...

So they dialed the case and found it was out of spec and ordered a new housing and filled it up with new parts. When I asked why they didn't just install a drop in complete unit, I was told that a drum to drum 9.25 wasn't available and they had to build them at the dealer from scratch. Sounded like a fairy tale to me but either way I had a new diff under my truck.

Of course they still managed to get into my wallet for a few hundred because the parking brake shoes were FUBAR and not covered under warranty. $125 a set for the shoes plus brake job labor now because that's a separate repair. I hate dealerships...

But the diff in mine is now silent.

Kevin

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My rear end builder says the Richmond gear sets like to howl.

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ok, so what exactly makes them howl? I have a set of 4:10 Richmond that howl like crazy. when everyone says they are not set up right, what is not right??

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I would think the checking depth on the pinion would be the problem. As to whether it is too deep or too shallow you can't see by simply looking at it.
As to how to get it out I don't think I would change the checking depth once the gears have been ran.
You can check the backlash and adjust it yourself with a dial indicator. I set the backlash years ago on one and never had an issue (removed an open carrier and installed a clutch pac)
I got a bad feeling the 391's I just set up are going to howl. I don't have them in yet and it may not be an issue but it was hinky trying to set the backlash...almost .003 difference measured on the ring gear at 4 different locations.