Re-aligning stock rear end gears

[droptopstang]

My rear end gears whine very loudly, and I am almost certain they are still the stock 3.55 gears. I have done gear installs in the past and have a full shop so putting in a new set is what I am looking at doing. However, have any of you ever had success with simply re-aligning the gears to get rid of whine? Assuming there are no broken teeth or anything like that when I get in there and look. Just wondering if its worth my time to just try and re-set them up or if I should just spring for a new gear set. The only thing I'm really trying to accomplish right now is to quiet them down for my daily driver use.

 

[mach828]

What are the characteristics of the whine? Only on accel, decel, coast, all the time, etc. Because that will help diagnose whats causing the whine. (backlash, pinion depth, preload) and determines how easy of a fix it is.

I just put used 3.55s in a Crown Vic this weekend, and they have zero whine. Even though most people will tell you that used gears will always whine, so only buy new.

 

[droptopstang]

They whine only on accel and insanely loud at highway speeds. Goes away completely when off the gas.

 

[NickD87]

I have the opposite, just got 4.10s put in and have whine on coast/decel (off the gas)
Shop says the pattern looked perfect and these are quiet compared to others hes done, he hasnt heard the noise though as it only starts above 50km/h
Any ideas?

 

[TexasBlownV8]

What has been done on the rear end to make the stock 355's whine? What's the history? Pinion seal change? Other work? Were these used gears installed in your housing?

Nick, 410's can be tricky to get right (there is a sweet spot for no whine on frpp 410s, if you know where it is AND if the gears are set up that way when new).

I have made changes to existing installs with whine, but most of the time, at least some of the noise stays, depending on how long the gears have run. And 410s are the worst!

Measure the backlash, see where you're at. Spec is .008-.012, or per some instructions, as high as .015. The higher the backlash, the more likelihood of whine at certain speeds.
If the whine is present at all speeds above some lower speed, you should look at doing a rebuild with new bearings, or at the very least check the backlash and see where it is. Of course the pinion could be out of whack too, but that usually results in growling and can show an off wear pattern.

If you do it yourself, please do it right (and safely of course). It is easy to screw it up, or "it got done" but you end up having noise.

 

[droptopstang]

I'm not sure what work has been done if any on the rear end. It looks like the pinion seal MIGHT have a very very slow leak to it, so maybe over time the fluid level decreased and the gears started wearing and developed the whine. I wont't be sure until I open it up. Or maybe seals were changed in the past and the carrier shims were not re-installed correctly...IDK

 

[mach828]

I would pull the driveshaft and tighten the pinion nut slightly. It only needs a slight movement, we are talking thousandths of an inch here. My guess is you need a little more preload, because when you accelerate its pushing the pinion gear into the ring gear and decreasing backlash.

If that doesn't cure your whine, you'll likely need to pull it apart.

 

[ChewyR]

Hey I hate to bring up an old thread but I didn't see a resolution here and I am having a similar problem. I have a faint but noticeable whine on acceleration only. I had installed 3.73 gears myself and no whine initially. I started with new gears, set pinion depth the same as the prior pinion, checked backlash and gear pattern. All looked good and no whine. I ended up breaking a couple teeth off the spider gears, so i to had to pull it apart, swapped in new spider gears. I didn't change the posi unit, and I found both teeth in the bottom of the rear end housing. So nothing that would change the ring and pinion setup. I didn't see any visible damage to the ring and pinion. But now I have a faint gear whine on acceleration only. So same question as original post, are my gears toast or is it possible I can reshim and/or correct the pinion bearing preload and expect that the noise will go away?

 

[Marble]

I didn't really see any answer for the OPs question.

In my experience, no one can ever answer that question until the rear is pulled apart and inspected by someone who knows their shit.

From what I've been told by gear mechanics in the past, it's a lost cause.