Hey guys,
I bought an evo off a auction, previous salvage title and i just started driving today. I'm hearing a grinding humming noise coming from the back of the car at about 30-40mph. It happens when i let go of the gas and its in gear. Best way to describe the sound is like a public bus when its driving beside you, it has that distinct humming grinding sound. That is exactly what it sounds like. I have no idea what it could be.

 

It would have to be an issue with the rear diff or driveshaft. I would try check the rear diff fluid and/or changing it with oem diaqueen.

 

I'd pull the fill plugs out of the gear boxes (total of 3) and check that they are full and that the lube looks to be in good condition. The saddest thing to do is to screw up a car when all it needs is some lube.