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3.73 gears hate me

 
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clay
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Location: South Carolina
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1972 Chevrolet Nova

PostPosted: Sat Feb 24, 2007 9:13 pm    Post subject: 3.73 gears hate me Reply with quote

About 2 weeks ago, I picked up a light bumping noise in the rear end. It was too slow to be anything I could think of and it ended up being an axle bearing (I think). I went ahead and tore everything apart to inspect since I was here anyway. I found a small surface crack in a tooth in the pinion. It wasn't all the way though the tooth, but you could snag it with a knife blade, so it was definately there. I went ahead and changed the ratio from 4.10 to 3.73 and this is where the post title comes in. This is actually the third time I have had a 3.73 in this rear end. The first time, I set it up just by the pattern like I had before and it screamed only in the 55 - 60 mph range. Above this it was quiet and below this it was quiet. I only drove the car for a mile and figured I needed to set it up according to pinion depth. I did this and had the exact same result. Called Richmond and they said I was describing the classic harmonic noise and it was a result of me not rounding the sharp corners on the gear teeth. I replied that wasn't in your installation instructions and if something needed to be done to the gear teeth, I figured you would do it. I figured that if it was just some slight interference with the corners it would wear in and get quieter, which it didn't. I put the 4.10's back in and sent the gear set off to them. After about 2 months, they sent me a new on and I sold it to a buddy at work. After this latest go around, I bought a Summit series gear just to have something different (probably made by Richmond anyway) and rounded the gear teeth this time. It is way better and is very livable, but it still does make some noise. I guess it isn't possible for me to setup a 3.73 and it be quiet - it's the only ratio I have had any problem with so far. On another note, another problem that plagues me with this rear end is the large pinion bearing inner race spinning on the shaft. I have to take it apart every few years and replace the pinion shims because they slowly get chewed up until they get spit out. It looks like it just creeps slightly every time it gets under a high load. The 4.10's did it and the 3.73 Richmond gears showed signs of scuffing on the pinion shims after a few months of running. I have tried Loctite, a crush sleeve and a solid sleeve and have the same problem regardless. I went back with the crush sleeve this time and figured it would maintain its preload longer after it spun a little bit than the solid. We'll see. Clay
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af2
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Location: grassvalley, ca
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1933 Willys Coupe

PostPosted: Sat Feb 24, 2007 10:45 pm    Post subject: Reply with quote

Clay, is this on the Nova?
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clay
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1972 Chevrolet Nova

PostPosted: Sat Feb 24, 2007 10:47 pm    Post subject: Reply with quote

Yep.
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Big Dave
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PostPosted: Sat Feb 24, 2007 10:53 pm    Post subject: Reply with quote

Is the housing machined true with a solid welded bead around the tubes? It sounds like you may have a bent tube. (an alignment shop would know).

Deburring the gear teeth is a good step, and they used to state that in the set-up instructions. (though I have not put a gear in, in quiet some time now).

I used to use a Dremel tool with a stone, rather than the specified hand file since; if I had good hand eye coordination I would have chosen a career as a surgeon rather than as an engineer.


Big Dave
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af2
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Location: grassvalley, ca
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1933 Willys Coupe

PostPosted: Sat Feb 24, 2007 10:56 pm    Post subject: Reply with quote

The thing that bugs me is the speed it screams at. That is the harmonics speed on out of balance tires also. My son and I put a Summit gear set in his Blazer and had the Summit install kit bolts fail! Shocked
The ring gear chipped and could have been a disaster if it wasn't dealt with when the noise started. Almost sound like you're situation.
Still running the gear set with Chevy bolts and there is no noise even with the chipped gear.
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10sec.et
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1969 Oldsmobile Cutlass

PostPosted: Sat Feb 24, 2007 11:44 pm    Post subject: Reply with quote

are you installing a NEW pinion bearing and having it spin ? i have had good success with "pinging" the surface on the pinion with a center punch AND using red loctite.

you can check straightness of the axle tubes( toe, not camber) by dropping a plumb-bob in several locations along the axle, mark these locations on the floor, and check straightness of your marks. it beats pulling the axle to have it checked.

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af2 wrote:
It seems we can look at our magical Balls and come up with a fix?

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af2
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1933 Willys Coupe

PostPosted: Sun Feb 25, 2007 1:08 am    Post subject: Reply with quote

Clay, I have to say the crush sleeve will exit before any straight up shim and collar. With that said please don't go there! Stay with a collar set up. The HP. you are running will destroy a crush sleeve quickly!
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Knarley Darley
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PostPosted: Sun Feb 25, 2007 10:56 pm    Post subject: Reply with quote

Clay I do alot of gear changes in my shop and have been told that Richmond gears are just flat out noisey, plus I have personal experiance with them, but the noise is usually livable. I have never deburred the teeth. I will only install GM gears if it is a driver with stock exhaust because of the noise of after market gears. The GM make NO noise. So dont feel bad, I dont think you did anything wrong, rather it was the gear set. I have also set them up by pinion depth and had them be pretty noticable and then gone back and set them up by contact pattern (which turned out to be considreably dilfferent than their stated depth)and had the noise go away. I have never had the shim problem or the crush sleeve be a problem. The only other thing I can think of is the pinion bearing preload. If they are to tight it will make noise and the bearings will fail fairly quickly. Also make sure the carrier bearings have enough preload that the ring gear is not being pushed away from or miss aligning with the pinion under load.
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Hanz
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2003 Dodge Ram

PostPosted: Sun Feb 25, 2007 11:21 pm    Post subject: Reply with quote

Am I missing something here, don't the 'sharp edges' never touch anything? At least not according to a centered pattern... I do like Knarley suggests, side bearings a little on the tight side, and pinion bearing a little on the loose side, with a centered pattern and have never had a noise of any type...have put many a gear in...

Hanz

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af2
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Joined: 01 Sep 2003
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Location: grassvalley, ca
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1933 Willys Coupe

PostPosted: Sun Feb 25, 2007 11:31 pm    Post subject: Reply with quote

Hanz, Sounds like B.S. to me. I have never had this problem. Ever!!!! That is why I am scratching my head!!!!!!!!!!!!

De burring gears is done at the MFG. You should be able to install them and have many care free miles of the most abuse you can give them!!!!!!!!!!!!! Rolling Eyes Still scratching!
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Big Dave
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PostPosted: Sun Feb 25, 2007 11:39 pm    Post subject: Reply with quote

I debur them because these gears are cast in China and machined in Mexico and then heat treated. I don't want a stress riser forming. I agree there isnít an issue with noise.

Big Dave
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