Hello again Gents. Got a strange problem(I think?) in the form of a noise.....Let me explain....
At the weekend some of the jobs I did included reinforcing the diff mounts(all 3, one main front and two small rear, this I did using polyurethane in a tube) and changing the diff fluid. I got the fluid from Audi, and came in 1ltr white bottles with "axle oil" written on it. I made 3 guys at Audi reasure me it is the right stuff, so I'm sure it is. Anyway the rear of the car was raised on ramps the whole weekend while I did some other odds and sods. After draining the diff(only 1.4 ltrs came out...I'm putting this down to the seals sweating oil for 11 years!) I filled it with 1.8 ltrs. I did this when the car was level and filled it untill oil started to pour out of the fill plug, as I was advised by an Audi Tech. Now before I changed the fluid the diff was not making any noises it shouldn't. As soon as I had it off the ramps on Monday, I took it for a test drive. Everything was A ok apart from a brand new noise coming from the Diff(as far as I can make out). Its very faint, almost like the whine of straight cut gears or driving your car in reverse. The noise is drowned out even if I put the heating on full whack. To add to this, its only noisy when you are applying the throttle(both under load or no load), and as soon as I lift off/rolling with no throttle the noise dissapears. The function of it is fine, doing its job as well as it always has. So far I have checked the level of oil in the diff, which is where it should be. I have also changed the wheels/tyres to make sure it wasnt road noise. I am 99.9% certain it is not a bearing because I know what a failed WB sounds like. All I have done is changed the oil and now I have this bloody noise!!! Can somone please help, and or advice. Any help will be immensely appreciated!