I have developed a metallic squeaking/scraping sound that is coming from the back. I haven't fully investigated, but I think it's either the rear u-joint or something in the rear brakes. I can make the noise louder when I press on the gas, which tells me it is definitely something spinning on the drivetrain - as opposed to exhaust, heat shield or something that doesn't really move/spin when the gas is pressed. So, what do you all think I should do to verify? And the u-joints don't have any oil, grease or other maintenance procedure I am neglecting, do they?