Why do my gears whine in cold weather only?

[Rash]

So, I have fairly loud whine on coast between about 52 and 40 mph. Definitely gear whine since it immediately goes away on even the lightest throttle. Here's the thing -it's only in cold weather. Right now, it's about 20-30 degrees here in NC and it's very obvious. When the temp gets about 50, it's much less noticeable, and above 60 or so - gone, can't hear it at all.

Any thoughts on why that would happen? I'm figuring it could be gear oil related. BTW - it's factory diff and gears (second one actually - first diff was replaced for various reasons).

 

[Steps]

Who replaced it? Did they use the wrong fluid? Have you checked to make sure it is not leaking since they tore into it?

If you can, take it back to them and tell them to fix it.

 

[Wyld]

Motives are known to whine...

 

[Rash]

Ford replaced the whole diff - new, unopened from the factory. This was after they tried unsuccessfully to fix gear whine on accel in original gears. They managed to make it worse and also create a vibration (which turned out to be the driveshaft), so they just replaced the whole thing. The whine I have now is much better, but pretty annoying IN THE WINTER ONLY! I really don't want anyone messing with the gears anymore unless I can be sure it'll help. I can live with the whine for the 3 months or so it's cold enough to cause it down here. But if changing fluids or something else other than replacing the gears will help, I'm all ears.

 

[Wyld]

Just curious but what MPH did the vibration kick in?

edit - nvm just saw the drive shaft.
http://s197forum.com/forum/showthread.php?t=11905

 

[TexasBlownV8]

Well, I think in the old days, that would be caused by fluids that were too thick, so when cold, they wouldn't flow as easy and make more noise.

But as mentioned, I'd check the fluid level, as it could be low.

 

[Steps]

And if you decide to change fluid I would suggest Royal Pruple. Do a search and you will fiind a lot of info on what folks are running in their diff.

 

[Rash]

Well, I think in the old days, that would be caused by fluids that were too thick, so when cold, they wouldn't flow as easy and make more noise.

But as mentioned, I'd check the fluid level, as it could be low.

If I'm not mistaken, there's no way to check the diff fluid level other than feeling with your finger to see if it's topped off. If it's not, you just add more fluid till it is, correct? Or should I just take off the cover and change the fluid?

 

[TexasBlownV8]

NO! Take out the plug and stick one of your smaller fingers down in the hole. Fluid should be below hole-level by about half an inch or so. If you can't get any fluid on the tip of your finger by sticking it down in the hole, then you may be low. (Do this at your own risk, dont get your finger stuck!).

And +1 on Royal Purple. I run the 75W-140 in mine.

 

[Rash]

NO! Take out the plug and stick one of your smaller fingers down in the hole. Fluid should be below hole-level by about half an inch or so. If you can't get any fluid on the tip of your finger by sticking it down in the hole, then you may be low. (Do this at your own risk, dont get your finger stuck!).

And +1 on Royal Purple. I run the 75W-140 in mine.

So if it's low, what's the best way to add it?

 

[Lime1Gt]

I use a plastic ty-rap, bend the end 3/4" roughly and insert to check the level.

You can use a suction pump to fill the diff. You can usually buy them where they sell grease guns as they use the same body parts.

 

[BigEdJr]

I think it's just your car freezing it's balls off...

 

[KIMMER]

Low fluid or too thick of fluid. I'd guess thick fluid due to the whine going away as it warms up. Switch to a synthetic like amsoil or royal purple. I run amsoil in my stuff, just make sure it is compatible with the limited slip. I still have to change mine over, but use amoil Severe Gear 75W-140 and then you need to add Traction-Lok axles add 4oz of friction modifier Ford part No
XL-3 or equivalent meeting Ford spec EST-M2C118-A if you have trac lock.

 

[Rash]

Low fluid or too thick of fluid. I'd guess thick fluid due to the whine going away as it warms up. Switch to a synthetic like amsoil or royal purple. I run amsoil in my stuff, just make sure it is compatible with the limited slip. I still have to change mine over, but use amoil Severe Gear 75W-140 and then you need to add Traction-Lok axles add 4oz of friction modifier Ford part No
XL-3 or equivalent meeting Ford spec EST-M2C118-A if you have trac lock.

Thanks, I'll look into that. It's going in for some warranty work, so I'll just have them check the fluid level. if it's not low, I'll change the oil.

My only concern with the Amsoil Severe is that, if it's thicker, wouldn't that possibly make it worse? If the (possible) problem is that the cold whether is causing the oil to thicken, thus reducing it's lubricating ability, thus causing more noise, then a more viscous oil would be even worse, right?