Help with '07 TRD 2WD

My truck recently started making a sort of whining noise, almost like the noise NASCAR's make when they let off the gas but a whole lot quieter. First thought is a wheel bearing going bad but usually in that case it goes away when you then one direction or another. Also, not sure if the two are related or not, but I've noticed over the last 2 out 3 weeks where I park in my yard the grass is dying under where my motor sits. There's no spot at work on the concrete so I know it's not oil and I haven't smelled antifreeze. Any ideas on either of these and do you think the two problems could be related?