Evening folks, just after some advice.
My 07 zed has done a little over 86k miles. In the last month or so, I've noticed a noise which seems to be coming from the rear of the car. It becomes apparent from about 40mph in 3rd gear, it's a low hum that gets louder as the speed increases.
I've been changing all fluids as I go, and at the weekend I changed the oil in the diff. I was hoping this might either quiet, or get rid of the noise entirely, but no luck. The oil that came out was darker, but clean and no shiny bits, so I'm unsure if the noise is coming from the diff. I'm more familiar with wheel bearing noises, and I'm not getting any change in noise when turning.
Any ideas? No noticeable noise under 35mph, is it likely to be a bearing or something inside the diff making the noise? Is there a chance I'm completely off base and it's the gearbox?