The dreaded 3.73 Gear whine...

Tyler72

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So, like many others, my Boss also exhibits gear noise from the 3.73 rear end. It starts at 60 MPH and stops at about 80 MPH. This is terrible for interstate driving because that's where you are always at. If I turn the radio up loud or roll the windows down it's not so bad, but with the windows up its very annoying. I honestly don't want Ford messing with it. I have set up hundreds of 8.8's and I know that its a tedious process to do correctly. I don't want some Joe Blow tech learning on my car. I don't want to take it back 10 times until they decide to just replace the entire axle and start the process over. Quite honestly I'd rather just buy a Ford Racing gear and a master install kit and do it myself so I know it's right. However... I did just order 3 qts of Amsoil 75w-140 severe duty gear oil. I was wondering if you guys think that may help it out? It's definitely gear noise and not a bearing issue, so my thoughts are it could help but I'm really not sure.

I also thought about pulling the cover (as opposed to just pulling the drain plug on my finned cover) and checking the pattern and backlash with some marking compound. But usually once a gear wears in wrong, its never going to be right without replacing it. Although I have been able to "correct" a few sets that were installed wrong before.

Your thoughts?
 
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NOGI88

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I got the same problem on my boss. It's not real noticeable but I know it's there. I'm going to a t56, so I'm just gonna do 410s. Hope it goes away then..
 

Tyler72

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From my experience... its not pinion preload issues. It's very much load related which indicates a pattern issue. It's not a bearing noise. In my past experiences, every single time there was a bad bearing or too much preload, the noise would be there whether loaded or not and got louder and higher pitched as speed increased. This is only between 60-80 mph and under light load. Goes away when coasting.
 

kxt

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I wouldn't change the gear, i'd just check it and see if its out of spec and try to fix what you got.
 

nosympathy

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Now, I will say I have not had gear whine period on my car. I swapped to 3.73 FRPP gears and had a local mustang only shop do it, as I wanted it done right and they were a great price and have a major reputation.

that being said. I had the swap done when I was mostly stock, never got gear whine. Now completely redone suspension and still no whine.

What I can tell you, is I had royal purple 75w-140 put in at the time and seemed like great diff oil. I then swapped that out not long ago for Red Line lightweight shockproof 75w140 and it was insanely different drive. The diff feels 10X smoother. I have heard that the stuff you have is amazing. So basing off my experience, if your still running the stock motorcraft stuff, I'd give it a shot. That amsoil is supposed to do wonders.
 

Tyler72

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and if there is too little preload?

Usually that results in pinion slop and a leaky pinion seal. Usually... I guess its possible to have just a tad too little and cause the pinion to shift sideways under load and alter the pattern, but if that's the case its not much because the seal has never leaked a drop! That said, it doesn't take much to cause a gear to make noise.

I may just go ahead and pull the cover and look at it. Not like its a big deal to reseal it and go on. The least I can do is check backlash and pattern.
 

burke985

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I put severe gear in my car and it only helped a little. I get the same between 60-80. Its annoying sometimes and sometimes its not there at all. Ill probably switch to 3.55's once the blower goes on
 

rextang

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my '11 3.31 GT with 47k mi has developed a noise issue too under light load between 65-80. Took it to the dealer for diagnosis today. It is most prominent after the car is warmed up so had to leave it there for them to drive. It started raining heavily just as the noise was heard, so they are postponing diagnosis until the weather clears. They can't tell if its gear related or carrier bearing. The sound is a faint, higher pitched pulsing sound at steady throttle on the highway.
 

me32

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The fluid will probably not make a difference since its a hardware issue. If you got mikes on it sounds like the only way to fix is with a new set of gear s
 

mantis118

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Mine has whined since it was new. Most of the newer 3.73 cars I have ridden in had the same noise. Even brought it to 2 different dealers and was told its normal...
 

jojobee

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From my experience... its not pinion preload issues. It's very much load related which indicates a pattern issue. It's not a bearing noise. In my past experiences, every single time there was a bad bearing or too much preload, the noise would be there whether loaded or not and got louder and higher pitched as speed increased. This is only between 60-80 mph and under light load. Goes away when coasting.

I dont have enough knowledge to agree or disagree with you but think i am affected by this issue too­
My 3.73 gears always whined a bit, i could hear them while cruising.
It was slightly annoying but very tolerable.


I recently added a 1 piece ds and guess what, i feel like im running a turbine under the car.
Where it becomes interesting is that i cannot reproduce the noise with the car on posts and adv track off. The wheels are spinning but the noise is simply not there.

Now is where i need your input as you clearly know a lot more than me about this.

My whine is always present when the car is in motion with load.
It increases with speed and is high pitched like a turbine.

I have a feeling my ds is now accentuating this noise to an unacceptable level.

Can you give me your theory as to what part combination could cause this noise in my case ?

I will either bring it to Ford to have them check it out or simply have my local shop switch to 3.31.



It could also be incorrect pinion pre-load.

I dont know what that is but i guess a Ford tech should be able to verify that.
In any case i assume they have to open the diff.

Usually that results in pinion slop and a leaky pinion seal. Usually... I guess its possible to have just a tad too little and cause the pinion to shift sideways under load and alter the pattern, but if that's the case its not much because the seal has never leaked a drop! That said, it doesn't take much to cause a gear to make noise.

.

Mine doesnt leak either but the whine...oh men!
 

UnleashedBeast

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I'm an Amsoil guy, and I'm here to tell you, Severe Gear 75W-140 isn't going to make a difference. If you want to quiet the rear gears, use this and never look back.

Red Line Heavy Shockproof

I didn't notice any difference in mpg efficiency or added sluggishness, but man were the gears so much quieter.
 

nosympathy

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I'm an Amsoil guy, and I'm here to tell you, Severe Gear 75W-140 isn't going to make a difference. If you want to quiet the rear gears, use this and never look back.

Red Line Heavy Shockproof

I didn't notice any difference in mpg efficiency or added sluggishness, but man were the gears so much quieter.

Why the heavy vs the lightweight? I currently have the lightweight in mine and think it is fantastic compared to royal purple. At what power level would we really need the heavy shockproof? Or for those of you with gear whine need heavy?
 

saleen homer

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I just had mine into the dealership. They replaced the ring and pinion, pinion bearing and seals. brought it home, no more noise, but sounds like the axle is coming out of the rear end. Very loud clunking noises coming from the rear. Taking it back soon.
 

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