Hello Everyone,

Last year, I had a friend replace the entire suspension, new brake pads, new drilled and slotted rotors, new 15" AR rims with Nitto 555r's, swapped the 9 bolt for a 10 bolt, and beefed up the 10 bolt with Nitro aftermarket diff cover, Motive gears, and auburn posi (3.73). By the time I got it back, winter came and I was not able to drive it much until recently. I had maybe 300 miles on the car and started hearing this whistle/vibrating noise yesterday for the first time. I panicked, went home and flushed the rear diff this morning.

The rear diff flush has the GM posi-additive plus I used the Lucas 80w-90 GL5 equivalent gear oil. Anyways, I drained it, filled it back up (till it came out of the fill hole) and took it for a spin. I thought that it would take awhile for this noise to disappear, so I took it for a spin around the neighborhood. Here is the audio clip of the sound.

Audio:
https://dl.dropboxusercontent.com/u/...1%20135840.m4a

Keep in mind that there is a lot of rattling noise from my crappy dash, but you can distinctly hear the howl as a high pitch noise that seems to be consistent "somewhat" with the speed.

I noticed that this sound does not happen during a rapid acceleration, but does happen sometimes when the throttle is engaged slightly. I noticed at times that I did not have the pedal pressed, there was no sound except for slowing down at low speeds. That is where is it weird. If I am already in motion at a certain speed and ease off of the throttle, it is fine. If I keep the pedal slightly depressed, it makes that noise. You can hear me playing with the throttle to make it happen in the audio clip.

So I am a bit worried that this is one of a few things. I could only hope that this is a wheel bearing, but it almost seems to resonate through the center of the car at times. My fear is that the issue is either a drive shaft issue or even possible that there is a problem with the pinion in the new rear end. Worst part about the work is that my supposed friend who worked on this for me is no longer a friend for which we had a big falling out. Anyone know what this noise might be? To be clear, this had not happened until around 300 miles after all the work had been done.

Any help is greatly appreciated! Thanks!

 

Check the torque on your pinion nut.

 

Yea, check the pinion nut first. Don't drive it any more than you have to.

 

To be fair to this board, I had to circle back and post up what happen since the howl.

The long story short, I had the whole effing thing rebuilt. I should have bought a Strange 9" for the cash I threw down on this repair alone. The issue in the end was the pinion and gear. Not sure why it failed, could have been from an improper break in period or defect. I suspect it might have something to do with having this work done in the winter, leaving the fluids in there and not having it fully broken in and flushed, but who knows.

In the end, my horrible howl was due to a severely worn pinion and ring gear. Thanks everyone for the help. I had to at least post up a final reply. I hate reading threads with questions that no one completes.

 

Thanks.