Gear noise at hwy speeds, rebuilt 400,000 mile differential

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Duluth, GA
I am concerned about the Amsoil Severe Gear 80W-90 in my 1992 Previa N/A RWD's differential. I had the bearings redone in it about 10 months ago. At the time I filled it with Amsoil Severe Gear 75W-110 and the groaning was more metallic in sound, as in it sounded more like metal to metal contact. Not exactly contact per se, but rather it sounded like a ringing that comes from metallic clatter. Either way, I switched over to Amsoil SVG 80W-90, which reduced the noise, but it did not completely deaden the noise.

Now after 6 plus months of driving with Amsoil SVG 80W-90, I'm tempted to either go back to conventional gear oil or possibly go with half SVG 80W-90 and half SVG 75W-140.

I am planning on draining the differential's SVG 80W-90 and getting a UOA done on it. Then refill with basic conventional 80W-90 until the results come in. If the results show good wear numbers I'll go with half and half of SVG 80w-90 and SVG 75W-140.

The reason why I want to continue to use the Synthetic Gear Oil is because my differential has such a low capacity at 1.6 quarts. When driving on the freeway at 80+ mph the differential gets up to 235 degrees F in ambient temperatures of 90+ degrees F. (IR Thermometer shooting rear of differential) I drive those speeds in hot weather 5 days out of the week where I live. I could change out my differential fluid more often, but I'd prefer to do it once a year at most. I drive approximately 20,000 to 25,000 miles a year.

What are your recommendations? I have seen UOAs of Amsoil SVG and have heard testimonials on BITOG and want to have the ultimate protection for my daily beater vehicle.
 
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12,482
Location
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The rear end may have needed more than bearings. Inspect. I had my truck rebuilt by east coast gear. They do excellent work. They do as some other rear end companies do, recommend non synthetic.

East coast pushes Lucas gear oil. I just can't bring myself to purchase much less let a bottle of anything Lucas near my vehicles.

I'm using Valvoline non syn in mine.
 
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4,585
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I don’t think the fluid is the issue. I suspect the gears aren’t set right. Differentials are pretty tough and will handle a lot of abuse, but will still have a shortened life if the gear mesh is incorrect. I’ll bet the magnet in yours is already showing debris. Did they give you a warranty on the work?
 
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You had the "bearings done" 10 months ago and the noise appeared immediately after?

Sounds like the job was not done properly the first time.

If your differential is getting that hot, you will want to use the thicker oil.
 

apham8

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Duluth, GA
Thanks for the replies, I will go ahead and go with a 80W-90 conventional for now and get a UOA for the Amsoil SVG 80W-90.

The job was done with a mechanic friend of mine. He didn’t charge me anything to do the job since I helped him with it. But he never rebuilt a differential before. He rebuilds transmissions and engines, so it’s not as if he wouldn’t know how to set backlash. Either way, it was his first rebuild, so who’s to say something wasn’t off?

The whirring noise is ONLY between 60 - 70 mph and when I take my foot off the accelerator. That is to say that when the differential is not under load it makes a noise.
 
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Yeah. Sounds like pinion lash is off a bit. But, if it’s only during decel like that, it can probably be driven 100k before it shows any other issues. we had a Chevy with a munched differential from being rear-ended, never had it fixed, and when we sold it, the whine was no worse than 10 years prior.
m
 

apham8

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Duluth, GA
The whirring noise is ONLY between 60 - 70 mph and when I take my foot off the accelerator. That is to say that when the differential is not under load it makes a noise.

Sorry, I am mistaken, I just took a short drive and the noise is only on acceleration between 60 - 70 mph. Take my foot off the gas and the noise gradually diminishes. It is virtually silent before and after that speed range. But when I get within the speed range, applying the accelerator brings about this distinct whirring noise that has been there since the rebuild. It has not gotten worse or changed in anyway. Like I said, it's been about 10 months and it does not affect the drive at all.

Switching from Amsoil's SVG 75W-110 to SVG 80W-90 improved the sound, so perhaps a higher viscosity will help deaden the noise.
 
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2,879
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Malaysia
You may need to consider 85W140 conventional .
Suspect the rebuilt wasn't done right , whatever your friend's credentials .
 
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23,065
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CA
The rear end may have needed more than bearings. Inspect. I had my truck rebuilt by east coast gear. They do excellent work. They do as some other rear end companies do, recommend non synthetic.

East coast pushes Lucas gear oil. I just can't bring myself to purchase much less let a bottle of anything Lucas near my vehicles.

I'm using Valvoline non syn in mine.
This is slightly off-topic, but this is not the first time that I have heard this. What is their rationale for recommending non-synthetic gear oil?
 
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JHZR2

Staff member
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45,332
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New Jersey
I agree that it may be something more/different than bearings. There are also bearing preload requirements that come into play.

We never had issues with our 04 Previa, and ran 75w-90 syn.

I did have to get a 4.10 LSD in my 91 BMW done twice - the first time a shop didnt really set it right, and I had diff whine. Even the second rebuild, from a reputable BMW builder, still had some whine.

The solution? It was actually Specialty Formulations Diff Oil, I think it was some racing variant. Redline and others didnt help before that. A good rebuild plus that fluid made the diff quiet for the next 80k or so through when I sold it. That car was in a flood early in its life, and probably had some damage early on.
 

MolaKule

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Iowegia - USA
Without proper bearing preloads (proper shim thicknesses inserted) NO differential lubricant is going to cure this noise. A higher viscosity lubricant may help somewhat by deadening the noise but a higher viscosity lubricant will only result in a temperature rise in your differential.

Save your money on the oil analysis and have a specialist in differential rebuilds take a look at the differential. He will have the proper mechanical gauges to set the gearing and bearing preloads.
 
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12,482
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North Carolina
This is slightly off-topic, but this is not the first time that I have heard this. What is their rationale for recommending non-synthetic gear oil?

They claim that non syn clings better to the gears, and handles water better.

I have asked Molakule if there is anything to this, and he states there is no reason not to use a synthetic gear oil, after break-in.

Here is their article, they also do push the Lucas, I'm guessing they have some deal.

 

apham8

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25
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Duluth, GA
Well, I switched to the East Coast Gear Supply recommendation of Lucas 85W-140 and the whine is still there at 60 - 70 mph.

The Amsoil Severe Gear 80W-90 I had in there had only about 15,000 miles and had metal shavings already. Not sure if it's normal to have metal shavings with that few miles on the differential fluid?

My plan is to keep running the Lucas 85W-140 with frequent fluid changes. I'm hoping the differential will last for sometime since I already invested the time and money into replacing the bearings. Again, the sound has not changed in about 10 months.

MolaKule, are you suggesting that I'm better off running synthetic versus this heavy weight of 85W-140? Perhaps, Amsoil 75W-140? Or try Schaeffer's 293 75W-90? I'm willing to try anything at this point, but would like to keep the experimentation to a minimum since I've already changed the fluid in this differential several times.
 
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High Tax Illinois
No gear oil will quite gear whine if something is not set right. Might dull it, but that's it. Just because somebody can rebuild engines/transmissions does not make them a expert on differentials installs. I know 20yr mechanics that won't touch rear differentials. You've gone 16 months of driving it without failure. Does it still make metal fuzzies on the drain plug? Going this far and it hasn't exploded yet seems to be a good thing. Put in gear oil your choice and keep running it. Good Luck!!!!!!
 

apham8

Thread starter
Messages
25
Location
Duluth, GA
No gear oil will quite gear whine if something is not set right. Might dull it, but that's it. Just because somebody can rebuild engines/transmissions does not make them a expert on differentials installs. I know 20yr mechanics that won't touch rear differentials. You've gone 16 months of driving it without failure. Does it still make metal fuzzies on the drain plug? Going this far and it hasn't exploded yet seems to be a good thing. Put in gear oil your choice and keep running it. Good Luck!!!!!!

This afternoon when I drained the Amsoil Severe Gear 80W-90 it had some metal debris on the magnet. Nothing too big, but there was debris and the fluid only has about 15,000 miles on it. Also, it did have little metal flakes suspended in the fluid.

MolaKule, you said that running 85W-140 will likely increase my operating temperatures, but I wonder if my differential is now operating at a higher temperature because of the improper rebuild? I am using an IR thermometer gun and I register between 200 - 230 degrees F. Depending on the ambient temperature. But that seems elevated from what I've read online. 200+ degrees F seems to be associated with heavy load or towing.

So I have a choice to make: Run synthetic gear oil that can withstand the possibly elevated temperatures that I'm seeing or run conventional gear oil and change frequently?
 

MolaKule

Staff member
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21,589
Location
Iowegia - USA
My recommendation is to run conventional gear oil until you get the gear loading corrected.

Notice the shimming with correct thicknesses that have to be selected.


 
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apham8

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25
Location
Duluth, GA
Thanks MoleKule for the response. We did this with the marking compound. It checked out per the Factory Service Manual.

I have a suspicion that the pinion and ring have been worn in some kind of way that is causing the noise. Mind you, the differential had 400k miles on it! That’s when the bearings were replaced. So it is a worn out unit.

I just did a run this evening at 80+ mph with ambient temperature of 81 degrees F. I registered 220 degrees F on the back of the differential. I’m concerned if conventional fluid is ok at that temperature? I drive like this, 80+ mph, daily and ambient temperature is 90+ degrees F.

I am likely going to keep running this differential just as it is until it gives up, which I hope it doesn’t. Honestly, I cannot invest more into it. I’d be better off getting into another vehicle.

Right now, I’m leaning towards Schaeffer’s 293 75W-90, which is about $10-$11 locally per quart and changing twice per year.
 
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