Noisy Gears?

[ohio5.0]

I picked up a 98GT from a guy at work to use as my DD. He was the original owner and it only has 76K miles. He did not beat on it at all. Under load the rear end (?) sings pretty loud. When you let off the gas it gets much quieter. I asked him about it and he said its been doing it since about 40K miles. I'm not sure where to start but I'll get under it this weekend. Any ideas would be appreciated!!

[Dirtyd0g]

Probably a bad pinion bearing.
Alan

[GREAZY]

I have seen a few of these cars doing that. They never used to do it until they started putting synthetic fluid in them from the factory. My 98 is noisy as well.

[ohio5.0]

Thanks guys!

[NXcoupe]

Could be the pinion is not preloaded enough or the backlash is not correct. When it sings on load, that means the pattern is not centered on the gear teeth.