Gear whine after rear diff fluid change.

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I have a 2002 Explorer with an independent rear differential. I replaced the original fluid with Supertech 75W-140. Now I get a little gear while. It's not super loud, but it's noticeable now.

Even tho the grade is the same on paper, do you think a name brand would eliminate the whine? Valvoline SynPower, Mobil-1 and Royal Purple Max Gear are readily available where I live. These all have the friction modifier already in the bottle. I had to add a bottle of the Ford XL-3 with the Supertech.

Any advice would be appreciated.
 
I would think thick fluid would quiet it. Add some Lucas.

I put 30% Lucas in my 4 speed and it did quiet the worn out front and rear ball bearings. Also have it in the diff.
 
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SuperTech should behave about the same as any really. There are subtle differences in wear performance between that brand and using the premium Amsoil Severe Gear diff oils, but not in noise. You could try a thick Amsoil diff oil or another synthetic brand -140.
Question: So you're sure you have a limited-slip diff, since you put in the friction modifier??? (No friction modifier if no limited slip type diff.)
 
With GM limited slip additive, supposedly you are supposed to add the limited slip additive first and before that to have shaken it for 3 minutes. Don't know what the Ford requires but assuming your's is a limited slip, I would make sure you followed all the steps and put in the correct amount of LS additive.
 
Originally Posted By: turtlevette
I would think thick fluid would quiet it. Add some Lucas.
I put 30% Lucas in .....

Yeah thats got to be the answer, go up in viscosity. So you're talking about Lucas 'Oil Stabilizer' right?
Anybody try a bit of LiquiMoly MOS2 in small dose in a diff? Does that hurt anything? Maybe quieter?
 
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Originally Posted By: ExMachina
You could try a thick Amsoil diff oil


Like what, their straight 190 weight, or 250 weight racing gear oils??

These did not work for me, in fact they made the gear whine worse yet.
frown.gif


The current 75W-140 Severe Gear is about the quietest this diff has ever been with the current gear set in it.
smile.gif
 
Originally Posted By: dailydriver
Originally Posted By: ExMachina
You could try a thick Amsoil diff oil

Like what, their straight 190 weight, or 250 weight racing gear oils??
These did not work for me, in fact they made the gear whine worse yet.
frown.gif

The current 75W-140 Severe Gear is about the quietest this diff has ever been with the current gear set in it.
smile.gif


No, I should have been more clear. I'd always want some VI spread in a diff. So, I meant don't use Amsoil Severe Gear 75w-90, but instead use 75w-140, the thickest possible here in this application. Of course, adding Lucas Oil Stabilizer is going to jack up the viscosity! Thats why I was wondering if anybody has tried MOS2 or Ceratec in a diff before.
 
What fluid was in it before? Drain the ST and replace it with the same brand and weight as the previous fluid.
 
Thanks for the replies. I'm the 2nd owner, and it was never changed before. I just did it at 96K, so it was whatever FOMOCO used. The spec is 75w-140 full synthetic right from the manual.
 
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I had this issue on my 91 318i. A rebuild solved most of the noise, meaning that it was mainly mechanical, but even after that, using specialty formulations gear oil kept it quiet when various flavors of redline and other lives couldn't.

It's kind of like the whole "Mobil 1 oil makes my engine louder" debates that come up from time to time. For the most part it's nothing, and probably couldn't be analytically determined, but sometimes people really do think they're on to something, and maybe in some cases they are!

I'd be mainly concerned with a mechanical issue that was perhaps brought to light with some service. Not sure how/why, just is. Because repair quieted my diff in a way no fluid could.
 
Originally Posted By: dave123
Many people had good luck with Schaeffer 267 to fix gear whine.

Schaeffer 167 is the one in the 75w-140 category, and has a PAO base with molybdenum. Might work. I'm ready to concede maybe changing brands alone might get rid of gear whine.
 
Originally Posted By: ExMachina
Originally Posted By: dave123
Many people had good luck with Schaeffer 267 to fix gear whine.

Schaeffer 167 is the one in the 75w-140 category, and has a PAO base with molybdenum. Might work. I'm ready to concede maybe changing brands alone might get rid of gear whine.
Yes I know that but I did and many have and used 267 in this app and many more to fix noise. 167 is only available in 5gallon pail unless that has changed 267 is available in Qt's.
 
Me,I wouldn't use Super Tech anything,especially gear oil. Maybe drain and refill with Motorcraft 75W140 and the Motorcraft additive (if it's required).
 
I'm pretty sure the rear ends of that time frame in the Exploders and Mountaineers were not all that robust to begin with. We had a 2005 Mounty with the 4.0 and it had the gear whine on light acceleration from 50-62mph since we bought it at 9k miles. Traded it in at 105k and the whine was no better or worse, despite me trying a couple of different fluids.

They apparently were built with the whine as a factory standard option on some vehicles.
 
FWIW those rear ends are known for making noise. We have rebuilt countless units and replaced a bunch of ring and pinions. More than once we have had to rebuild the differential and replace both axles, rear bearings, hubs and rear knuckles to get the noise to go away.
 
Did the whine start immediately after the oil change or did it start after a few miles?
 
THanks for the funny comments!

I think it started right after the change. It makes noise when I maintain a speed limit, but goes away when I let off the gas, or get on the gas. Again, it's not super loud, but it's there. I think I remember the diff being pretty hot one day I was messing with the driveshaft. I think a high quality oil would be good piece of mind at least.

I did some oil research last night, and the most preferred are the Amsoil, Mobil 1, and I think Redline from what I can tell.
 
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