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  #1  
Old 03-09-2001, 04:53 PM
mshelly mshelly is offline
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Angry

Has anyone had trouble with noisy 8-3/4" 3.91's from U.S. Gear?

I called them on it and they will not stand behind what they sell! And these were not cheap.

Even if they have to select for quiet ones and charge a premium I would understand, but to just ship them and then shrug their shoulders is wrong!

Should I try another brand or are they all giving the "aftermarket vs OEM" excuse?

Steamed Mike.
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  #2  
Old 03-09-2001, 05:03 PM
cdignition cdignition is offline
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If your gear is making excessive noise, it was not installed correctly(there is a chance it was not lapped properly from the factory, but well assume theyre right). I installed mine, first one i ever did, and it was perfect from the start....Just have to pay attention to details...
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  #3  
Old 03-09-2001, 05:14 PM
mshelly mshelly is offline
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The noise is not excessive but audible on light power at low speeds.

I believe it to be setup correctly. They did suggest a slightly different drive/coast pattern but I'm not hopefull and neither are they by their own admission.
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  #4  
Old 03-09-2001, 11:16 PM
PLUM CRZY PLUM CRZY is offline
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WOW!!...thats like the first complaint I've heard about US Gear. Six months back I put a 8-3/4 third member in my challenger. It has a US Gear. In looking for the unit and calling shops, everyone said stay away from Richmond Gear cause they make noise and are more difficult to set up. Just about all the shops recommended US Gear. I havent had a problem with mine yet. Maybe you received a bad gear or have an improper set up.
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  #5  
Old 03-10-2001, 12:27 AM
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FuryusVIP FuryusVIP is offline
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Unhappy My 3.91 makes noise also...

My 3.91 from US Gear also makes a little noise. The bearings where all replaced during the gear change. I have noticed that some of the aftermarket gears do vary from batch to batch, but I only began to notice the noise after I changed the cam to something a little milder.
My Gear change was done by a pro, but we all have bad days...
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  #6  
Old 03-10-2001, 03:21 PM
440fied 440fied is offline
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Default gear noise

Hey Mike! The after market vs oem is valid. If you want a quiet gear for the street go with oem. The metal used is a little differant(softer). If for the strip or other type of racing after market is the way to go,a little stronger(harder)a little noisy!
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  #7  
Old 03-10-2001, 05:52 PM
cdignition cdignition is offline
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Just to verify on gear hardness:

OEM gears are the hardest available, followed by aftermarket street gears, then pro race gears are the softest....
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  #8  
Old 03-11-2001, 06:26 PM
djswwg djswwg is offline
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Thumbs up more gear noise info

Almost always, gear noise is a result of incorrect initial set-up. It's possible to have a set of gears that were either improperly machined or lapped in before final hardening, but it would be rare, especially if the maker in question (US Gear) tends to be reputable and makes quality products. By your description of the noise you have, I can almost assure you that incorrect adjustment is the problem. You can try re-adjusting to get a better pattern, but usually once a set of gears has been driven the noise becomes "built in" to them and is permanent. It has been my experience that most guys spend enough time to get the pattern "real close", but don't go the extra mile to get it perfect because they are just dying to put the car back together and go stomp on it to see how much more snort the new ratio gives them. (been there, done that!) So that's the bad news. The good news is that even if you have a bit of noise the gears will likely last a good long time and not give any problems. Another thing to try is using a very heavy grade of gear lube. 75W90 is the norm, find something with higher viscosity and try that. Good luck....djs
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  #9  
Old 03-12-2001, 09:42 AM
fox fox is offline
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Default gear noise

What do you think of this ??? I remember reading this years ago as a cure for gear noise. Take the ring and pinion out and put them in the oven for 2 hrs. and then let them cool overnite. Will it work or will it soften the metal too much??? Has anyone done this with positive results?? Every one with opinions please respond!!
fox
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Old 03-12-2001, 10:18 PM
djswwg djswwg is offline
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Red face

I sincerely doubt that 600 degrees would have any effect on them. Probably an old wives tale. If someone has done this, I'd sure be interested in hearing what the results were!......djs
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  #11  
Old 03-13-2001, 01:09 AM
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pishta pishta is offline
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I just heard a speed shop guy say to media blast the gear set and set it back up, drive around a few miles and it will "re-seat" itself. Sounds too easy, and a little far fetched. Are gears hardened? and if so, will media blasting them remove the hardening? I got a singing 3.91 too, but it is an OEM job, probably been around the world twice considering the shape of the van I got it out of. I checked lash and pattern and they are right on.
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  #12  
Old 03-14-2001, 11:40 PM
djswwg djswwg is offline
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Smile gear noise

Pishta-be sure it isn't a bearing worn out that's noisy. If you aren't real familiar with diff noises, sometimes it can fool you. Also, fresh lube often help dampen diff sounds. Just 2 cents worth; hope it helps!......djs
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  #13  
Old 03-15-2001, 12:14 AM
PLUM CRZY PLUM CRZY is offline
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After reading all the responses, we dont even know what kind of noise this is!! Some one mentioned bearing howl. I hope we are not over looking the easiest noise to correct, Positraction Chatter (oops Sure-Grip Chatter). Change the lube to a heavy weight gear lube or a synthetic and add a bottle of the fiction modifier. Yes the ring and pinions are heat treated. More than likely its not a case hardened part, its treated down to the core. So a 600 degree temp in the oven wont do anything neither will media blasting. Heat treat temps are more in the lines of 1200 degrees and more! followed by some type of quench. When i bought my gear the place that did the set up said the first 100 miles are critical to the life of the gear. The gear gets extremely hot due to a work hardening process. The gear should be allowed to cool. If it overheats it will damage the gear.
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  #14  
Old 03-15-2001, 04:47 AM
mshelly mshelly is offline
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What we ended up with after experimenting with U.S. gears recommendations and conventional setup patterns is a low speed whine drive and coast, and a high speed howl on drive.

Used friction modifier with no effect. Everything is new except the posi unit.

The noise is not horrible but is noticeable over the exhaust. I guess what I have here will give good service, but am gun shy on future gear changes.

Thanks all for the suggestions.
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