[DanC]

I recently had my R&P changed out from 3.42 to 3.08 using a new "USA Standard Gear" set.

The setup starts to make an audible whine around 1800 rpm and goes away ~2150 rpm, more pronounced under accel/load, and horrendous and loudest at ~2000 rpm.

The installer states that the backlash and shimming is correct and trying different settings just changes the rpm range of the noise. He is also upset that he cannot get the setup to be quite like it should be and he has done "dozens" of the 8.5 GM setups and never had an issue until now.

Now I don't know if "it's just me" , but it seems like the whine is getting louder but staying in the same rpm range.

Any ideas here on why and what, if anything, can be done about this?

Thanks, DanC

1978 Firebird Espirt original 10 Bolt housing "PJ" (2.43 open)
Yukon Dura Grip YDGGM8.5-3-28-1 carrier
USA Standard Gear ZG GM8.5-308

[Keith Seymore]

Backlash and shim recommendations are just a starting point; the set up then needs to be tuned to get the correct contact pattern.

If it is truely a defective gear set and if it doesn't respond to repeated trials then the only recourse is to replace with another ring and pinion set.

K

[Half-Inch Stud]

Good to know if it has a constant drone (as if pinion depth is not where the gears were rung-in) or a cyclic drone (like as if not seated flush with diff Carrier flange.

If itsa a constant drone then let it ride into quiet with wear.

If itsa cyclic then look into a proepr seating or a better posi carrier.

[SRGN]

Use marking compound and check the pattern at 3 different points. If the pattern differs at any one of the points, it's likely a defective ring gear. I've seen a couple in the last few years. Since it was quiet before the gears, it's unlikely that the carrier has an issue. I've had a couple of carriers with excessive runout cause an issue with noise, I just spend the extra money on Eaton units for my vehicles these days. If you can post a picture of the pattern, it will be a lot easier to diagnose.

[mgarblik]

Did the shop doing the work have any comments about what the pattern check looked like when they were done setting it up? Very hard to comment without seeing the results of that check. I would like to see both a drive side and coast side check results. In general, the lower the numerical gear ratio, the easier it is to get a nice pattern and quiet operation. In my experience, GM ratios steeper than 3.73:1 are a little more difficult to make really quiet as the number of teeth on the pinion gear decrease. A 3.08:1 ratio, in theory should be fairly easy to set up. Of course, it's always possible the gear set is defective.

[SRR]

Make sure the pinion nut isn't backing off! This will destroy the diff. really quick. I've seen this twice.

[steve25]

Did all 4 new bearings go in on the gear swap?
Some new off shore bearings are crap.

I recall one case where the guy setting up the new gears got distracted and left the honed out set up pinion bearing in the rear!

[DanC]

Here are the answers to your replies, as best I can....

Originally Posted by Keith Seymore

Backlash and shim recommendations are just a starting point; *the set up then needs to be tuned to get the correct contact pattern.

If it is truely a defective gear set and if it doesn't respond to repeated trials then the only recourse is to replace with another ring and pinion set.

He did start with the indicated pinion depth and then fine tuned the pattern several times.

K

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Originally Posted by Half-Inch Stud

Good to know if it has a constant drone (as if pinion depth is not where the gears were rung-in) or a cyclic drone (like as if not seated flush with diff Carrier flange.


If itsa cyclic then look into a proepr seating or a better posi carrier.

It is a cyclic drone and actually that was another reason I changed the gears to begin with, but the main reason was to drop the rpms at cruise. The 3.42 was pretty noisy all the time that I only discovered after quieting the exhaust by getting rid of the Flowmasters. *So perhaps it could be the Yukon carrier?

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Originally Posted by steve25

Did all 4 new bearings go in on the gear swap?
Some new off shore *bearings are crap.

Yes all new, USA made Timkin and Koyo bearing and races were installed, including axle bearings.

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Originally Posted by mgarblik

Did the shop doing the work have any comments about what the pattern check looked like when they were done setting it up? *Very hard to comment without seeing the results of that check. *I would like to see both a drive side and coast side check results. *In general, the lower the numerical gear ratio, the easier it is to get a nice pattern and quiet operation. * In my experience, GM ratios steeper than 3.73:1 are a little more difficult to make really quiet as the number of teeth on the pinion gear decrease. *A 3.08:1 ratio, in theory should be fairly easy to set up. *Of course, it's always possible the gear set is defective.

He did mention the contact pattern *looked good on both sides. I do not have any photos.*

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Originally Posted by SRGN

Since it was quiet before the gears, it's unlikely that the carrier has an issue. I've had a couple of carriers with excessive runout cause an issue with noise, I just spend the extra money on Eaton units for my vehicles these days. If you can post a picture of the pattern, it will be a lot easier to diagnose.

Noise was another reason I changed the gears to begin with, but the main reason was to drop the rpms at cruise. The 3.42 was pretty noisy all the time that I only discovered after quieting the exhaust by getting rid of the Flowmasters. *So perhaps it could be the Yukon carrier? If it has excessive runout, would that not show up on the micrometer or pattern paint?

[mgarblik]

Thanks for answering all those questions. You mentioned the rear end was noisy with the other ring and pinion set as well. This leads me to the axle bearings. What are their condition? Axle bearings can transfer tremendous noise through the tubes at speed.

[HWYSTR455]

My Moser 12 bolt is noisy as heck, and I'm on my 2nd US Gear 3.42 ring & pinion in 5k miles. I did carrier bearings at that time too.

Maybe I should look at me axle bearings?

I called Moser (they did the rear initially) and they told me some gears are just noisier than others, not sure if that's true or not, but I'm going to install another set of them.

I have all new carrier bearings this time too, but was considering a different brand R&P.

I actually have a new True Track carrier too.

What should I look for on the axle bearings?



.

[SRGN]

Originally Posted by DanC

Noise was another reason I changed the gears to begin with, but the main reason was to drop the rpms at cruise. The 3.42 was pretty noisy all the time that I only discovered after quieting the exhaust by getting rid of the Flowmasters. *So perhaps it could be the Yukon carrier? If it has excessive runout, would that not show up on the micrometer or pattern paint?

On a noisy rear, I'll install the carrier without the ring gear at the right preload and use a magnetic base dial indicator to make sure it's true on the face that the gear bolts to. You will also see it in the pattern, if it's different at different checking points. The dial indicator is useful to determine if it's the gear or the carrier causing an issue.

[SRGN]

Originally Posted by HWYSTR455

My Moser 12 bolt is noisy as heck, and I'm on my 2nd US Gear 3.42 ring & pinion in 5k miles. I did carrier bearings at that time too.

Maybe I should look at me axle bearings?

I called Moser (they did the rear initially) and they told me some gears are just noisier than others, not sure if that's true or not, but I'm going to install another set of them.

I have all new carrier bearings this time too, but was considering a different brand R&P.

I actually have a new True Track carrier too.

What should I look for on the axle bearings?



.

If you have C clip retained axles, it's easy to check. Pull the axles and inspect the surface where the bearing contacts. If it's significantly discolored, grooved, or pitted, it's time for bearings and new axles. If you have C clip eliminators, you would have to press the bearings off to check the bearings. The Strange "street" c clip eliminators use a tapered bearing, their race units and Moser units have ball bearings and are notorious for leaking during street use.

[steve25]

So did the OPs noisy gears that got taken out show ware, and in particular show ware that would have lead to failure?

[Keith Seymore]

Bearings would be a low growl or drone or rumble.

Ring/pinion gear mesh is a high frequency pure tone (a howl or whine).

K

[HWYSTR455]

Originally Posted by Keith Seymore

Bearings would be a low growl or drone or rumble.

Ring/pinion gear mesh is a high frequency pure tone (a howl or whine).

K

Then mine is def a R&P singing.

I have the hybrid ends on the Moser housing, using a Ford big bearing (double row).

I bought it as a complete assembly minus brakes, broke it in as instructed, and it sang from day one. Yes, used correct fluid. They use US Gear exclusively. They don't list bearing brands on their' website, but I will look at the kit they provided and check the bearings.


.

[DanC]

Originally Posted by mgarblik

Thanks for answering all those questions. You mentioned the rear end was noisy with the other ring and pinion set as well. This leads me to the axle bearings. What are their condition? Axle bearings can transfer tremendous noise through the tubes at speed.

I changed out the axle bearings with Timken USA. BTW when the RH axle was pulled for the gear change the bearing fell apart! The bearings I originally bought were AC/Delco and made in China , and looked like the one that fell apart. So then I purchased and installed Timken's.

Originally Posted by steve25

So did the OPs noisy gears that got taken out show ware, and in particular show ware that would have lead to failure?

The pattern and condition of the 3.42 R&P look fine and I tried to attached two pics 180 out of both but was unsuccessful.

Originally Posted by Keith Seymore

Bearings would be a low growl or drone or rumble.

Ring/pinion gear mesh is a high frequency pure tone (a howl or whine).

K

Mine is definitely a high freq whine!

[Keith Seymore]

Originally Posted by HWYSTR455

Then mine is def a R&P singing.

I have the hybrid ends on the Moser housing, using a Ford big bearing (double row).

I bought it as a complete assembly minus brakes, broke it in as instructed, and it sang from day one. Yes, used correct fluid. They use US Gear exclusively. They don't list bearing brands on their' website, but I will look at the kit they provided and check the bearings.


.

When I was in the driveline development group at Truck we would say "a singing axle is a happy axle".

K

[b-man]

Originally Posted by DanC

The pattern and condition of the 3.42 R&P look fine and I tried to attached two pics 180 out of both but was unsuccessful.

Try cropping your pics slightly, that should stop them from turning sideways or upside down.

[PontiacHO]

Originally Posted by DanC

I recently had my R&P changed out from 3.42 to 3.08 using a new "USA Standard Gear" set.

The setup starts to make an audible whine around 1800 rpm and goes away ~2150 rpm, more pronounced under accel/load, and horrendous and loudest at ~2000 rpm.

The installer states that the backlash and shimming is correct and trying different settings just changes the rpm range of the noise. He is also upset that he cannot get the setup to be quite like it should be and he has done "dozens" of the 8.5 GM setups and never had an issue until now.

Now I don't know if "it's just me" , but it seems like the whine is getting louder but staying in the same rpm range.



Any ideas here on why and what, if anything, can be done about this?

Thanks, DanC


1978 Firebird Espirt original 10 Bolt housing "PJ" (2.43 open)
Yukon Dura Grip YDGGM8.5-3-28-1 carrier
USA Standard Gear ZG GM8.5-308

I’d start asking the folks that did the work some questions….
Rotating torque the pinion pre-load was set at?
Did they use a new never used pinion nut for final assembly?
Did they preload the carrier bearings for final assembly?
What was the final assembly backlash?
Did they send you a photo of final assembly pattern?

If you get vague and or no answer, then they don’t know what they’re doing.

[burd]

I’d take it to a good rear end shop.