I purchased the car 4 months ago and was on the highway today when it downshifted(cars an automatic) and started hearing this whining grinding sound, it only happens when you accelerate or decelerate. When Accelerating it just grinds and whines. when decelerating it whines very LOUD. car does not make the noise in park or neutral and does not do it while revving it up in neutral or park


any input pleasee!

 

You need to look at the drive line. Jack up the rear, grab and shake the drive shaft, spin the rear wheels by hand and listen for any noises. If you have any serious clunks when you shift to drive or reverse you may have a U joint failure. Grinding and squeaking will come from the wheels/brakes. The parking brake shoes inside the rear rotors are sometimes a problem.
Ed

 

I've also seen on RWD cars and trucks the pinion bearing in the differential go bad and cause the same symptoms. Usually when it goes bad, though, you get a pretty good loss of gear lube out of the pinion seal/bearing. I've even seen some that when you grab the driveshaft back by the flange/rear u-joint it will move the pinion flange back and forth or around in a circle. The times I've had u-joints go bad I've had either a serious driveline vibration or a squeak at low speeds.

 

Thanks guys! Well I had a chance to look at it today in the day light and near the real axle it looks like a light of grease has built up, could this be anything?

 

I forgot to mention the center carrier bearing on the driveshaft, which can whine and whir and grind.
You need to be more descriptive about the grease build-up.
Ed

 

Well I hopped under the car and checked the rear differential fluid and it was bone dry, I have since filled this and noticed it is leaking. But even after filling it the car still makes the whining noise when lifting off the accerlator

 

Its beyond repair...sadly