QuestionThe noise started out as a shrill noise in the rear end at about 45 mph, it would stop/quiet when not accelerating.. now it is a terrible, scary metal grinding noise that seems to have travel from rear to middle of car. Obviously,something is very wrong, no smoke and still drives ok.. help.. I'm very scared of what may have happened.
AnswerAWD? If AWD and since it goes away when coasting, I believe that it lies in the rear differential- a bearing, most likely a pinion bearing is going out. The sooner it is repaired, the less damage will be done, but it doesn't sound like it will be a cheap fix. Like usual, the best way to find the problem is to get under the vehicle, and since the tires need to be moving at a good clip, it should be up on a vehicle lift.
If it's front wheel drive, it only leaves the brakes as being speed-dependant, although the noise would usually be when applying the brakes or all the time...
Don't wait for this to fail, if its the rear differential, when it locks up you will likely go for quite a ride, similar to applying the emergency brakes, but more effective and leaving you stranded right where it happens. The inspection will be cheaper than a tow.
