Rebuilt Diff Whining, now what?
Race Director
Joined: Sep 1999
Posts: 11,360
Likes: 382
From: Plano TX
Thread Starter
Melting Slicks
Joined: Feb 2003
Posts: 2,529
Likes: 27
From: Auburndale Florida
2025 C2 of the Year ('64-'66) Finalist - Unmodified
St. Jude Donor '03-'05-'06-'07-'09
Looks like we are going to install a new ring and pinion. This time from US Gear and staying with the 3.55 ratio.
Just want a good set up that's quiet!
Thanks to all who posted. Will update when I get the diff back and installed in the car in a couple of weeks.
Just want a good set up that's quiet!
Thanks to all who posted. Will update when I get the diff back and installed in the car in a couple of weeks.
Race Director
Joined: Sep 1999
Posts: 11,360
Likes: 382
From: Plano TX
Safety Car
Joined: Nov 2008
Posts: 3,716
Likes: 551
From: Seattle Washington
The old design 3.55 gear used a 9-32 ratio, 32 ring gear teeth and 9 pinion teeth. Very strong but created a lot of heat and were a little noisy until they were fully broke in. Which usually didn't take long. The angle of the teeth from the low tooth count on the ring gear caused increased wear when compared to other ratios which used a 37 tooth count.
The new 3.55 gears use 11-39 ratio. Noise is rarely an issue with them and never on decel. Providing they were set up correctly. Decel noise is nearly always cause by incorrect pinion depth. A pattern check would have confirmed this.
Improper break in may also cause the noise BUT the noise at cruise or light acel would be much louder. Changing to a 3.70 gear won't cure a bad set up.
Mike
The new 3.55 gears use 11-39 ratio. Noise is rarely an issue with them and never on decel. Providing they were set up correctly. Decel noise is nearly always cause by incorrect pinion depth. A pattern check would have confirmed this.
Improper break in may also cause the noise BUT the noise at cruise or light acel would be much louder. Changing to a 3.70 gear won't cure a bad set up.
Mike
Drifting
Joined: Jun 2012
Posts: 1,990
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From: Port St. Lucie Fl
Melting Slicks
Joined: Jul 2006
Posts: 2,285
Likes: 487
From: Salmon Arm, BC
The most common mistake when setting up Richmond gears is doing the pattern check with the wrong backlash. If you set pinion depth for the best pattern using .006-.007 backlash the are going to be noisy. Richmond gears are honed for .010 backlash and you must compensate for that.
Mike
Mike
Last edited by OMF; Dec 25, 2015 at 12:53 AM.
Drifting
Joined: Jul 2002
Posts: 1,995
Likes: 110
From: Garland Texas
Proper break-in technique has almost nothing to do with the gears. You're not going to break in a new gear set in 100 miles. With the poor quality of the surface of the teeth on nearly all new gear sets, the best you will accomplish is knocking down the high spots. One exception is the REM polished gears I put in Paul Dana's diff. The REM polishing does work. I wish I could use polished gears on every diff I build.
Break-in deals more with the pinion bearings. You can burn up the bearings in a fresh rebuild in 10 minutes. That's why they always say no constant highway driving for the first 100 miles. A new set of bearings, set at the correct preload, with no load, with heat up in less than 15 minutes at 800 rpm. They will heat up much faster at 400 rpm. (Rpm of the driveshaft/pinion gear) Below 500 rpm there is no circulation inside the diff. The front pinion bearing gets very hot very fast.
Pinion bearings need two heat cycles. First test drive should be less than 15 minutes around town under 30 mph. Take it home and park it for 24 hours. Second heat cycle should be twice as long, faster than the first but not constant highway speed. Keep changing speed, accel, deccel, moderately. Park it for 24. After that then take it easy for 100 miles.
Carrier side bearings aren't quite so tender. I have never seen a burned up side bearing. But I have seen plenty with excessive wear. Side bearings rely on splash for lubrication. So running the diff even a pint low is hard on them.
How long before the first lube change? It depends on if the clutches were pre-seated or not. If they have not been pre-seated I would find the closest parking lot and do a lot of very slow, tight circles in each direction. Then drive home very slow and change the fluid. The amount of metal that comes off each clutch disc is staggering. It will also turn the fluid black very quick.
If the clutches were pre-seated, properly, change the fluid in a hundred miles. If running without preload springs, give it two hundred miles.
Mike
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Safety Car
Joined: Nov 2008
Posts: 3,716
Likes: 551
From: Seattle Washington
I have no desire to get into another oil debate!
Proper break-in technique has almost nothing to do with the gears. You're not going to break in a new gear set in 100 miles. With the poor quality of the surface of the teeth on nearly all new gear sets, the best you will accomplish is knocking down the high spots. One exception is the REM polished gears I put in Paul Dana's diff. The REM polishing does work. I wish I could use polished gears on every diff I build.
Break-in deals more with the pinion bearings. You can burn up the bearings in a fresh rebuild in 10 minutes. That's why they always say no constant highway driving for the first 100 miles. A new set of bearings, set at the correct preload, with no load, with heat up in less than 15 minutes at 800 rpm. They will heat up much faster at 400 rpm. (Rpm of the driveshaft/pinion gear) Below 500 rpm there is no circulation inside the diff. The front pinion bearing gets very hot very fast.
Pinion bearings need two heat cycles. First test drive should be less than 15 minutes around town under 30 mph. Take it home and park it for 24 hours. Second heat cycle should be twice as long, faster than the first but not constant highway speed. Keep changing speed, accel, deccel, moderately. Park it for 24. After that then take it easy for 100 miles.
Carrier side bearings aren't quite so tender. I have never seen a burned up side bearing. But I have seen plenty with excessive wear. Side bearings rely on splash for lubrication. So running the diff even a pint low is hard on them.
How long before the first lube change? It depends on if the clutches were pre-seated or not. If they have not been pre-seated I would find the closest parking lot and do a lot of very slow, tight circles in each direction. Then drive home very slow and change the fluid. The amount of metal that comes off each clutch disc is staggering. It will also turn the fluid black very quick.
If the clutches were pre-seated, properly, change the fluid in a hundred miles. If running without preload springs, give it two hundred miles.
Mike
Proper break-in technique has almost nothing to do with the gears. You're not going to break in a new gear set in 100 miles. With the poor quality of the surface of the teeth on nearly all new gear sets, the best you will accomplish is knocking down the high spots. One exception is the REM polished gears I put in Paul Dana's diff. The REM polishing does work. I wish I could use polished gears on every diff I build.
Break-in deals more with the pinion bearings. You can burn up the bearings in a fresh rebuild in 10 minutes. That's why they always say no constant highway driving for the first 100 miles. A new set of bearings, set at the correct preload, with no load, with heat up in less than 15 minutes at 800 rpm. They will heat up much faster at 400 rpm. (Rpm of the driveshaft/pinion gear) Below 500 rpm there is no circulation inside the diff. The front pinion bearing gets very hot very fast.
Pinion bearings need two heat cycles. First test drive should be less than 15 minutes around town under 30 mph. Take it home and park it for 24 hours. Second heat cycle should be twice as long, faster than the first but not constant highway speed. Keep changing speed, accel, deccel, moderately. Park it for 24. After that then take it easy for 100 miles.
Carrier side bearings aren't quite so tender. I have never seen a burned up side bearing. But I have seen plenty with excessive wear. Side bearings rely on splash for lubrication. So running the diff even a pint low is hard on them.
How long before the first lube change? It depends on if the clutches were pre-seated or not. If they have not been pre-seated I would find the closest parking lot and do a lot of very slow, tight circles in each direction. Then drive home very slow and change the fluid. The amount of metal that comes off each clutch disc is staggering. It will also turn the fluid black very quick.
If the clutches were pre-seated, properly, change the fluid in a hundred miles. If running without preload springs, give it two hundred miles.
Mike
Drifting
Joined: Jul 2002
Posts: 1,995
Likes: 110
From: Garland Texas
Wow, that's a delicate question.
No, I am not a fan of synthetics. But I don't have anything against them either. It's just never been proven to me either way. If I was in a position to build and monitor two identical diffs and used under the same conditions, street or racing, then I would base an opinion. But it would be from what I discovered, not from a promotion.
I know Eaton does not want synthetic lube used because of the clutches. But I have been unable to get a clear reason why. 80-82 corvettes and 84 up use a completely different clutch design which cannot chatter. 85-96 Dana 44's use the same bearings as the 63-79 Eaton diffs so synthetic can't be an issue there.
In my opinion if you are going to run synthetic, start with synthetic.
Mike
No, I am not a fan of synthetics. But I don't have anything against them either. It's just never been proven to me either way. If I was in a position to build and monitor two identical diffs and used under the same conditions, street or racing, then I would base an opinion. But it would be from what I discovered, not from a promotion.
I know Eaton does not want synthetic lube used because of the clutches. But I have been unable to get a clear reason why. 80-82 corvettes and 84 up use a completely different clutch design which cannot chatter. 85-96 Dana 44's use the same bearings as the 63-79 Eaton diffs so synthetic can't be an issue there.
In my opinion if you are going to run synthetic, start with synthetic.
Mike