adjusting the diff?

[euroZ06]

Hi,

So about 3 years ago i bought 489 case and all new 3.55 gears/posi. I had a shop in NY put it together for me, however, ever since they did it, its been making a howling sound. Its not very severe, but its audible. I usually hear it when cruising/off gas, when I'm accelerating, its quiet. So it seems like they didn't set the gears correctly. I tried various liquids to no avail. I only put about 3-4k miles on it, so hopefully nothing is worn too bad. It is not super loud, I have to point it out to people to hear it, but once i do, they do hear it.

I have since moved from NY, and now I'm in Miami and I'd like to address this. The only problem is that around here I DO NOT TRUST any shop to do any work (feels like they can't even change the oil properly). Unfortunately, i live in a building, and I'm not allowed to do mechanical work, so i can't even take off the diff.

There is a bolt on the front side of the diff (where the driveshaft attaches), does that bolt regulate anything? I likely only need a small adjustment, so curious/hopeful that it will adjust anything. If so, should i tighten or loosen and how much... thanks. 

[John_Kunkel]

The pinion nut retains the u-joint yoke and also adjusts the pinion preload. If it's not loose enough to allow noticeable play in the yoke, there's nothing you can do with it to correct the noise.

Deceleration gear howl/whine is the most common type of gear noise, it is caused by faulty gears or improper installation. After it's accumulated a few miles, adjustment won't usually solve the problem.

[ACUDANUT]

The pinion nut retains the u-joint yoke and also adjusts the pinion preload. If it's not loose enough to allow noticeable play in the yoke, there's nothing you can do with it to correct the noise.

Deceleration gear howl/whine is the most common type of gear noise, it is caused by faulty gears or improper installation. After it's accumulated a few miles, adjustment won't usually solve the problem.

I agree. Its normal

[Kern Dog]

The pinion nut retains the u-joint yoke and also adjusts the pinion preload. If it's not loose enough to allow noticeable play in the yoke, there's nothing you can do with it to correct the noise.

Deceleration gear howl/whine is the most common type of gear noise, it is caused by faulty gears or improper installation. After it's accumulated a few miles, adjustment won't usually solve the problem.

I agree. Its normal

He didn't state that it was normal, just that it was the most common noise.
You either live with it or replace the gears.